More Baking Problems Solved (Woodhead Publishing in Food Science, Technology and Nutrition)

More baking problems solved Stanley P. Cauvain and Linda S. Young Published by Woodhead Publishing Limited, Abington H...

Author: Stanley P Cauvain

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More baking problems solved Stanley P. Cauvain and Linda S. Young

Published by Woodhead Publishing Limited, Abington Hall, Granta Park, Great Abington, Cambridge CB21 6AH, UK www.woodheadpublishing.com Woodhead Publishing India Private Limited, G-2, Vardaan House, 7/28 Ansari Road, Daryaganj, New Delhi ± 110002, India woodheadpublishingindia.com Published in North America by CRC Press LLC, 6000 Broken Sound Parkway, NW, Suite 300, Boca Raton, FL 33487, USA First published 2009, Woodhead Publishing Limited and CRC Press LLC ß 2009, Woodhead Publishing Limited The authors have asserted their moral rights. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the authors and the publishers cannot assume responsibility for the validity of all materials. Neither the authors nor the publishers, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from Woodhead Publishing Limited. The consent of Woodhead Publishing Limited does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from Woodhead Publishing Limited for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. Library of Congress Cataloging in Publication Data A catalog record for this book is available from the Library of Congress. Woodhead Publishing Limited ISBN 978-1-84569-382-4 (book) Woodhead Publishing Limited ISBN 978-1-84569-720-4 (e-book) CRC Press ISBN 978-1-4398-0108-6 CRC Press order number: N10009 The publishers' policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp which is processed using acid-free and elemental chlorine-free practices. Furthermore, the publishers ensure that the text paper and cover board used have met acceptable environmental accreditation standards. Typeset by Godiva Publishing Services Limited, Coventry, West Midlands, UK Printed by TJ International Limited, Padstow, Cornwall, UK

Preface

In the manufacture of baked products we are dealing with ingredients and processes which have a `natural' background and are therefore subject to change. Such changes inevitably have an impact on the complex ingredientrecipe-process interactions which characterise the manufacture of baked products. This means that there is always a ready supply of new problems with baked products which need solutions. In addition to the natural variations that bakers have to cope with there are drivers for change from consumers, legislative sources and the desire for innovation. While these drivers may not directly create problems in baked goods qualities, they do challenge bakers' knowledge and ingenuity. We would argue that there is little difference between `problem solving' and innovation or new product development. Our premise is that both activities require bakers to have an intimate knowledge of many complex interactions and that there is little difference in finding solutions to a particular quality problem or identifying an appropriate route for new product development. By treating a quality improvement as though it were a quality defect it is possible to identify suitable courses of action for product development. For example, if a loaf of bread lacks volume then is diagnosing the causes of that defect so very different from asking the question `How do I make my loaf of bread larger?'. Since we wrote Baking problems solved we have become increasingly aware of the need for developing structures for arranging and storing knowledge to meet the different needs of bakers. Providing ìnstant' answers to problems is only one way to deliver information with value. In this volume we have continued to deliver some of those instant answers but also tried to provide fragments of information on different aspects of baking. To help new readers we have re-written Chapter 1 and included more information on knowledge

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structures and their development; processes which we believe are essential to the development of technical skills in baking. Apart from elements of Chapter 1 all of the information in this volume is new. In a number of cases the information provided in this volume is complementary to or extends that provided in Baking problems solved, so to help readers we have provided appropriate cross-references in, for example, the form `(BPS, pp. 1±2)'. Stanley P. Cauvain Linda S. Young

Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2

Problem solving: a guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 How to problem solve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 The record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 The analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Modelling techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Matching patterns and visualising changes . . . . . . . . . . . . . . . . . . . . 1.6 The information sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7 New product development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8 Some key ingredient and process factors affecting product quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flours and grains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 We have seen references to the ash content with white flours but this is not a figure that appears on the specification from our UK miller. Can you explain what the ash content means and should we ask for it to be determined on our flours? . . . . . 2.2 What does the term grade colour figure mean in flour specifications? How is it measured? What are the implications for bread quality? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Can you explain the functions of the different components in the wheat grain and, after milling, their contributions to the manufacture of baked products? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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We understand that millers often use a mixture of different wheats to manufacture the flours that they supply to us. Can you explain why they do this? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We have heard several experienced bakers talking about the `new harvest effect' and the problems that it can cause. Can you explain what is behind this phenomenon and how we can mitigate its effects? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We have the water absorption capacity of our flour assessed regularly but find that this is different to the actual water level that we use in the bakery. What are the reasons for this difference and is it important for breadmaking? . . . . . . . . . . . . . . . Why is the protein content of wholemeal bread flour typically higher than that of white flours but the bread volume is commonly smaller with the former? . . . . . . . . . . . . . . . . . . . . . . . . . . . We get a significant variation in the quality of our wholemeal bread and rolls depending on which flour we purchase. What characteristics should we look for in a wholemeal flour specification to get more consistent results? . . . . . . . . . . . . . . . . . . . Since enzymes such as alpha-amylase are inactivated by heat during baking, is it possible to use heat-treatment of flour to inactivate the enzymes in low Hagberg Falling Number flours before baking? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We are considering making traditional German-type rye breads and have researched the recipes and production methods. Do you have any suggestions as to what characteristics we should have in the rye flour? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We have changed suppliers of our self-raising flour and find that we are not achieving the same product volume as before. If we adjust the recipe by adding more baking powder, we find that the products tend towards collapse. Can you explain why and how do we overcome the problems? . . . . . . . . . . . . . . . . . . . . . . We are a bakery working with a local farmer and miller to produce a range of local breads and want to use some different varieties and forms of malted grains that we are producing. Can you advise us on any special issues that we should be aware of? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Can we mix oats or oat products with our wheat flours to make bakery products? If so, are there any special issues that we should be aware of? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We wish to add non-wheat fibres to some of our baked products to increase their healthiness. What fibres can we use, in what products and what potential technical problems should we be aware of? What is resistant starch and can it be used in bakery products? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Other bakery ingredients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 We wish to reduce the level of salt (sodium chloride) that we use in our baked products. What do we need to be aware of when making reductions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 What alternatives are there to using sodium chloride (common salt) in the manufacture of bread products? And how can we reduce sodium levels in our other baked products? . . . . . . . . . . . . 3.3 We have seen references to a `lag phase' for bakers' yeast; what does this mean and what are the implications for baking? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Are there any particular precautions that we should take in handling, storing and using bakers' yeast in the compressed form? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 What different types of bakers' yeast are available? Would there be any particular advantages for us to use an alternative to Saccromyces cerivisii in the manufacture of our fermented products? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 What effect does vinegar have on bread and why is it added? 3.7 What ingredients are commonly used as preservatives? Are there any particular benefits associated with different ones? . . 3.8 We have heard that alcohol can be used as a preservative. How is this achieved? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.9 What are the possible alternatives to chemically based preservatives? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.10 What type of sugar (sucrose) should we use for the different products that we make in our bakery? . . . . . . . . . . . . . . . . . . . . . . . . . 3.11 Can you explain some of the main features of alternative sugars to sucrose and how they might be used in baking? . . . . . 3.12 What are the differences between diastatic and non-diastatic malt powders and how can they be used in baking? . . . . . . . . . . . 3.13 We read a lot about the different enzymes that are now available and how they might be used in baking. Can you tell us what they are and what functions they have? . . . . . . . . . . . . . . . 3.14 How do anti-staling enzymes work? Can they be used in cake as well as in bread and fermented products? . . . . . . . . . . . . . . . . . . 3.15 Can you explain the different terms used to describe bakery fats? What are the functionalities of the different forms in baking? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.16 We want to make a range of bakery products using butter as the main or only fat in the recipe. Can you advise us of any special technical issues that we need to take into account when using butter? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.17 We are using butter in several of our bakery products which comes in chilled at about 4 ëC (as cartons on pallets) and are encountering problems with variability in its processing. We

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4

recognise that it is likely to be associated with the temperature of the butter when we are using it. What is the best way to treat the butter in order to get a more consistent performance? What are the differences between dough conditioners and bread improvers? What consideration should we take into account when choosing which one to use? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What is lecithin and how is it used in baking? . . . . . . . . . . . . . . . . What is meant by the term `double-acting' baking powder and what is the value of using such products? . . . . . . . . . . . . . . . . . . . . . We have been having some problems with the quality of our bread, pastries and biscuits, and one solution that has been recommended to us is that we should add a reducing agent to our recipes. Can you tell us more about reducing agents and how they function in baked products? . . . . . . . . . . . . . . . . . . . . . . . . .

Bread and fermented products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 What characteristics should we specify for white bread flour and why? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 We make crusty breads in a retail store and recently we have been having complaints about our products going soft quickly. We have not changed our recipe or process. Can you help us understand what has happened? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 We are not a large bakery but are planning to part bake and freeze bread products for bake-off at some later time. What points should we be aware of? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 When we re-heat par-baked products we find that they remain soft for only a short period of time, typically an hour or so, but they quickly go hard and become inedible. If we do not re-heat them we find that par-baked products can stay fresh for several days. What causes the change in the rate of firming? Is it the additional moisture lost on the second bake? . . . . . . . . . . . . . . . . . . 4.5 We have been freezing some of our bread products in order to have products available in times of peak demand. We notice that there is `snow' or ìce' in the bags when we remove them from the freezer. Can you tell us why this happens and how it can be avoided? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 We are seeking to improve the quality of our bread products and are getting conflicting advice on what the optimum dough temperature ex-mixer should be. Can you advise us as to whether we should increase or decrease our dough temperature? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 How can I calculate the amount of ice I need to replace some of the added water when my final dough temperature is too warm? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 We are considering the purchase of a new mixer for the

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manufacture of our bread using a no-time dough process. There are two types of mixer that seem to be appropriate for our plant production needs, the spiral-type and the CBP-compatible type, but before making our decision we need to understand any issues with respect to dough processing and final bread quality. Can you please advise us? . . . . . . . . . . . . . . . . . . . . . . . . . . . . We are looking to buy a new final moulder for our bread bakery. Can you advise us on the key features we should look for and how they might impact on final bread quality? . . . . . . . . We are having problems keeping a uniform shape with our bloomers. They tend to assume a bent or `banana' shape (Fig. 19). This happens even though we take great care to straighten them when they are placed on the trays. Can you explain why we get this problem? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Why is a bread dough piece coiled after sheeting? Does the number of coils achieved have any impact on bread quality? . We have been taught to always place the seam of our moulded bloomer dough pieces downwards on the tray before proof but we do not take the same precautions with our pan breads. Can you explain the relevance of placing the bloomer dough piece `seam' down? Should we also do this with our pan breads? . . . We have been having problems with holes appearing in different places in our pan breads. Can you explain where they come from and how to eliminate them? Is there any relationship between the holes that we see inside dough pieces coming from the divider and the problems that we are experiencing? . . . . . . . . We are making open-top pan breads and find that the top crust of some of our loaves is being lifted off during the slicing process. Sometimes there is a hole underneath the crust while on other occasions there is not. Do you have an explanation for this problem? We have tried making the dough stronger by adding more improver but without any reduction in the problem, in fact it may have been slightly worse. . . . . . . . . . . . . . Can we make bread without using additives? What will be the key features of the ingredients and process that we should use? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We have had bread returned to us by the retail store through which it is sold. They are not satisfied with the quality. We have some pictures of the products concerned. This seems to be a òne-off' and we are at a loss to understand what has led to the problem. Can you help us understand where the problem came from? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We have noticed that loaves sometimes break only on one side of the pan but that the break is not formed consistently on one side. Can you explain why this is? . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Contents 4.18 We are making a range of crusty breads using a small bread plant. We appreciate the value of having an open cell structure to encourage the formation and retention of the crust. However, from time to time we have difficulty in achieving the desired degree of openness in the structure. Can you help us identify why this happens? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.19 We make sandwich bread for a large customer and they are concerned about the crumb characteristics of the products. What are the important ones? How do I measure these? What steps can I take to control or improve on these? . . . . . . . . . . . . . . 4.20 During the manufacture of bread and other fermented products we sometimes have small quantities of `left-over' dough from a mixing, can we add these back to other mixings or re-use them in other ways? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.21 We make bread and rolls using a bulk fermentation process. Can we use ascorbic acid to improve our bread quality? . . . . . . 4.22 Our total time for bread production from flour to baked loaf is set for about 6 hours. Currently we use a bulk fermentation time of 4 hours and a final proof time of 90 minutes. We find that with increased bread sales we do not have enough proving capacity. If we were to shorten the final proof time, what other changes would we have to make to maintain our current bread quality? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.23 In breadmaking what is the difference between a sponge and a ferment and when would they be used? We have also seen references to barms, can you tell us anything about these as well? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.24 How would we prepare and use a sponge with the Chorleywood Bread Process? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.25 Our bread and buns prove to a satisfactory height in about 50 minutes but we get no additional lift from the products in the oven. We have tried increasing their strength and using more improver but, whatever we do, we see no oven spring. Do you have any ideas as to why we are getting no oven lift? . . . . . . . . 4.26 What is the purpose of `knocking-back' the dough when using a bulk fermentation process to make bread? . . . . . . . . . . . . . . . . . . . 4.27 We have two bread lines running side-by-side, with the same equipment bought at different times. We are using the Chorleywood Bread Process (CBP) and do not quite get the same volume and cell structure when making the same pan bread product. We compensate by adjusting yeast and improver level but do not get the same crumb cell structure. Can you help us understand what is happening? . . . . . . . . . . . . . . . . . . . . . . . . 4.28 We are experiencing a problem with loaves baked in rack ovens since we bought new pans. As the enclosed photograph

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Contents shows, they are joining together above the pans. The portions of the loaves that touch have no crust formation, which makes them weak when they are de-panned and handled. How can we prevent this from happening? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.29 We wish to create a bolder shape and more open cell structure with our crusty sticks and have recently increased our dough development by mixing longer. Now we experience problems with the products joining together in the oven. If we underprove the dough pieces, we have problems with ragged bread and poor shapes. Should we reduce our mixing time back to its original level? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.30 We are finding that the crumb of our bread is too soft for slicing. We also notice a tendency for the sides of the loaves to slightly collapse inwards. We do not think that conditions in our cooler have changed, can you please advise us on what to investigate? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.31 We have spiral and twin-arm type mixers and would like to produce a finer cell structure with our sandwich breads. Can you suggest ways in which we might achieve this aim? . . . . . . . 5

Cakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 What characteristics should we specify for cake flour? . . . . . . . . 5.2 We are experiencing some variation in cake quality, especially volume. How important is it to control the temperature of our cake batters? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 How do we calculate the likely temperature of our cake batter at the end of mixing and what temperature should we aim for? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 What do the terms high- and low-ratio mean when they are applied to cake-making recipes? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 We are looking to re-balance our cake recipes and have a set of rules that we work with. However, it would help us if you could explain the principles behind such rules of recipe balance as applied to cake making? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 We have been making cake muffins and find that when we cut them open they have large vertical holes in the crumb. Why is this and how do we eliminate them? . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7 Why do some of our cake muffins lean to one side during baking? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 We have been making a range of different cake sizes using the same plain batter and get varying quality results in terms of their shape and appearance despite having adjusted the baking conditions. Do you have any advice? . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9 We would like to change the physical dimensions of some our cake products to make different sizes and shapes. Do you have

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6

any advice that you can give us as to how to adjust the batter deposit weights for the different pan sizes? . . . . . . . . . . . . . . . . . . . Currently we add alcohol, in the form of spirits or liqueurs, to our celebration cakes after they have been baked and cooled. We leave them for a few days after treating them but this is taking up a lot of space. What advantages/disadvantages would there be if we added the alcohol to the batter before baking? . We are baking Genoa-type fruit cakes using sultanas and find that while the centre of the crumb is a nice golden yellow, around three sides of the cut face of the cake (the bottom and the two sides) the colour is much browner and darker. Can you help us identify the cause of this problem? . . . . . . . . . . . . . . . . . . . . We regularly measure the water activity of the individual components in our composite cake products and try to adjust them to reduce the differential between them to reduce moisture migration. Even though we do this we are still having problems keeping the cake moist during shelf-life. Can you give us some advice as to what we may be doing wrong? . . . . Why do some traditional cake-making methods specify a delay in the addition of the sodium bicarbonate and specify the use of hot water? Would this approach have any practical applications today? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We have recently changed the acid that we use for our baking powder mix and have adjusted the neutralising value accordingly. Subsequently we have been having some problems achieving the volume and shape that we want with our small cakes. Can you explain why we are having these problems? . . What are the factors that control the shape and appearance of the top of a cake? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We are seeking to reduce the level of fat that we use in some of our cake recipes but find that simply taking fat out adversely changes our product quality. What are the possibilities of using `fat replacers' to help us with our strategy? . . . . . . . . . . . . . . . . . . . We are using natural colours in our slab cake baking and find that we get variable results, not just from batch to batch but sometimes within a batch. Can you suggest any reasons for this problem? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Biscuits and cookies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 We have been trying to make soft-eating cookies and are having a degree of success with the recipe that we are using. The products are not expected to have a long shelf-life but we find that they are going hard too quickly. Can you suggest any ways of extending the period of time that the cookies will stay soft-eating? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

139

140

141

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144 145

147

149 150

150

6.2 6.3 6.4 6.5

6.6 6.7

6.8

6.9 6.10 6.11

6.12

6.13 6.14 6.15

Contents

xiii

What are Shrewsbury biscuits and how are they made? . . . . . . . What characteristics should we specify for our biscuit and cookie flours? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What are the main issues that we should be aware of in the manufacture of savoury puff biscuits? . . . . . . . . . . . . . . . . . . . . . . . . . We assembled a selection pack of biscuits and cookies, one of which is a rectangular product coated on the top with icing. When the pack is opened after some time this coated biscuit has a `bowed' shape, the base is soft eating but the icing remains hard. Can you suggest reasons for these changes? . . . . How important are the dough and batter temperatures in biscuit and cookie making? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We are experiencing dark brown specks on the surface of our plain sheeted biscuits. We have been using the same recipe for a number of years without a problem. Can you identify the cause of the specks and suggest a remedy? . . . . . . . . . . . . . . . . . . . . We are having some problems with packing our rotary moulded biscuit lines. When we measure the thickness of the biscuits we have noticed that some are thicker than others. Can you suggest any reasons why we should be getting such variations? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We are having intermittent problems with shrinkage of our semi-sweet biscuits after they have been cut out from the dough sheet. How can we stop this from happening? . . . . . . . . . Is it important to use a fermentation period in the manufacture of crackers? What effects are we likely to see from variations in the fermentation time? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We are experiencing blistering on the surface of our semisweet biscuits and sometimes see cavities under the top crust and little hollows on the bottom. Can you identify the possible cause of the problem and suggest a solution? . . . . . . . . . . . . . . . . . We are manufacturing short-dough biscuits using a rotary moulder and have been offered an alternative supply of sugar. We notice that the new sugar is more granular than the material we have been using previously; would this have any effect on biscuit quality? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Is it possible to reduce the level of sugar in our biscuit and cookie recipes without affecting their quality? What would be the alternatives to sucrose we could use? . . . . . . . . . . . . . . . . . . . . . . We would like to reduce the level of fat in our biscuit recipes. How can we do this? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We have installed a new cutting and creaming machine for the preparation of our sandwich wafers and re-furbished the production area. We have found that we are now getting intermittent problems with the wafer sheets breaking up on

152 153 154

155 156

159

160 161 162

163

164 165 167

xiv

Contents cutting. Can you offer an explanation as to why this might be happening? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

Pastries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 We have been experiencing considerable variability in processing our short and puff paste products; sometimes we have problems with paste shrinkage and on other occasions we get stickiness. We have checked our weighing systems and can find no problems with ingredient additions. We have no climatic temperature control in the factory or ingredient storage facilities, are these likely to be significant contributors to the problems? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 We are looking to start production of croissant. In my travels I have seen many variations on products that are called croissant. Why are there so many different forms and how are they made? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 What is the best way to use pastry trimmings? At present we are feeding them back into the sheeting stages . . . . . . . . . . . . . . . . 7.4 We are manufacturing savoury short pastry products that are blocked out to shape and lids by sheeting a paste with the same formulation. We wish to increase our production rate and are considering reducing or eliminating the rest periods in the production sequence. Can you advise us on their function and any consequences that we may face if we change them? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 What method should we use to calculate the water temperature to deliver a consistent final paste temperature at the end of mixing? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 We are making puff pastry, Danish pastries and croissant using all butter and often have problems with the processing of the pastes and feel that we do not get the best of quality from the final products. What are the best processing temperatures and conditions when using butter with such products? . . . . . . . . . . . . . 7.7 We would like to reduce the level of fat that we use to make our puff pastry but would like to retain pastry lift. Can you provide us with some guidance as to how we might achieve our objectives? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.8 Some of the short pastry cases that we make for restaurants to fill and serve have been returned to us as being `mouldy' on the base. We were surprised, as we thought that the water activity of the shells was too low to support mould growth, and when we examine the bottom of the pastries we can see that there is a discoloration but we do not think that it is mould. Can you identify what has caused the discoloration and how to eliminate it? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

168 169

169

171 174

175 176

177

178

179

Contents 7.9

7.10

7.11

7.12 7.13

8

We are having problems with the custard tarts that we make. The pastry shell is very pale coloured but if we increase the baking time, we find that the custard filling is not very stable and shrinks away from the case during storage. If we raise the baking temperature, the custard filling boils and breaks down during storage. Can you give us any advice on how to get a better pastry colour without causing problems with the filling? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We are experiencing distortion of our pastry shapes. We have measured the shrinkage but find that it is not even. We have also noticed that the laminated products are experiencing some variation in product lift. What might be the causes of these problems? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We have been receiving complaints from customers that our short pastry which we use for meat pie products has an unpleasant eating character that they describe as `waxy'. The comments are most often related to the base pastry in the pies. Why is this? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We have been trying to freeze fully proved croissant for later bake-off. Can you identify the important criteria for their successful production? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What characteristics should we specify for the flour that we use for making savoury and sweet short pastes? We make both fresh and chilled unbaked paste products. . . . . . . . . . . . . . . . . . . . . .

Other bakery products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 We are freezing a range of unbaked, chemically aerated products including scones and cake batters and now want to include some variations using fresh fruits. We have carried out a number of trials and have a range of issues that are mostly related to the fragility of the fruit. Can you provide some advice? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 We have been asked to improve the sensory qualities of our scones and have been able to do this by a number of recipe changes. While these changes have been largely satisfactory for our plain scones, the fruited varieties we make still tend to be too dry eating. Do you have any suggestions as to how we can make them more moist eating? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 We make and bake scones on a daily basis. Recently we placed them unbaked in a refrigerator but the baked quality was poor. We used a retarder instead but we still found that the products were small in volume. Is it possible to retard unbaked scones and still produce an acceptable product? . . . . . . . . . . . . . . . . . . . . . . 8.4 What are Staffordshire oatcakes and how are they made? . . . . . 8.5 What are Farls and how are they made? . . . . . . . . . . . . . . . . . . . . . .

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181

183 184 185 186

186

188

189 190 191

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Contents 8.6

8.7

8.8 8.9

8.10 8.11

8.12

8.13 8.14

8.15 8.16

We are producing a variety of finger rolls using white flour. The rolls must be soft eating and retain their softness for several days; to achieve this we are using a roll concentrate. To help us cope with fluctuations in demand we freeze a proportion of our production but find that the defrosted product is very fragile and may even fall apart. Can you help us overcome this problem? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We want to add freshly baked deep-pan pizza to the product range that we sell through our bakery shop. We do not want to make small quantities of dough throughout the day for their manufacture but when we try to work with a larger bulk of dough we find that the variation in quality is too great, even when we refrigerate the dough in our retarder. What would be a suitable way for us to make the bases? . . . . . . . . . . . . . . . . . . . . . . What are the key characteristics of cake doughnuts and how do they differ from other types of doughnut? . . . . . . . . . . . . . . . . . . . . . We have been producing a range of cake doughnuts that are iced with various flavoured coatings. In order to cope with peak demands we have taken to freezing a quantity of the products. We have observed that progressively during storage a crystalline growth appears on the products. When they are defrosted, the growth disappears. Can you identify why this happens? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We have been approached by some of our customers asking if we can make gluten-free breads. How could we do this and can we match the quality of our regular bread products? . . . . . . . . . . We are not getting the quality of finish that we would like from the fondant we are using. Often the finished products lack gloss. Can you give us some tips on how to improve our use of the fondant? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Can you tell us something about Chinese steamed breads and their production? We make our standard breads using the Chorleywood Bread Process, would we be able to make these products using this process? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What is cinnamon twist bread and how could we make it? . . . . We have been experimenting with retarding fruited rolls and buns. We find that the smaller products are quite satisfactory but loaves made using the same formulation and baked in pans have `stains' around the fruit pieces and a darker crust colour than we would like. Can you please advise us on how to cure these problems? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . We are retarding rolls in our retarder-prover and find that they lean to one side and lose weight during storage. Can you advise us as to how to cure these problems? . . . . . . . . . . . . . . . . . . We want to extend the mould-free shelf-life of our flour

192

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201 202

Contents

xvii

Tortilla but when we try to make the dough more acid we have processing problems. What options could we consider for achieving our aim? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 8.17 In reading about the manufacture of hamburger buns we see references to the pH and TTA of the brew. What do these terms mean? When are they used and what is the purpose of controlling them? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 9

What is/are/why/how? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 What is meant by the term `modified atmosphere packaging' and how can we use this approach in the production of baked products? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 We have seen references to the Milton Keynes Process but can find very little technical information on the process. Can you tell me what it is (was) and how it is (was) used? . . . . . . . . . . . . 9.3 Can you explain the principles of vacuum-cooling of baked products and its potential applications? . . . . . . . . . . . . . . . . . . . . . . . . 9.4 I have heard the terms `glycaemic index' and `glycaemic load' used when describing bakery products. What are they and what is the difference? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5 What are pro- and pre-biotics and how can they be used in our bread products? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Can you please explain the difference between hydration and hydrolysis? What is their relevance to the manufacture of baked goods? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7 What is meant by the term `glass transition temperature' and what is its relevance to baking? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8 What is the Bohn's spot test and what is it used for? . . . . . . . . . 9.9 What does the term MVTR mean when applied to packaging and what is the relevance to baked products? . . . . . . . . . . . . . . . . . 9.10 We have heard people referring to synergy in the use of ingredients in baking processes, what is this process and can you identify any examples? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.11 What are polyols and how are they used in baking? . . . . . . . . . . 9.12 What value is there in measuring the colour of bakery products and how can we carry out the measurements? . . . . . . . . . . . . . . . . . 9.13 What is acrylamide? Where does it come from and how do we limit it? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.14 How can we measure the texture of our bread and cakes? Currently we use a hand squeeze test for bread and apply a `score' to the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

205

223

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

225

205 207 208 209 211 212 213 214 215 217 218 220 222

1 Problem solving: a guide

`You can't solve a problem with the same type of thinking that caused it' Einstein The quote from Einstein may seem like a statement of the obvious but after many years of experience in the baking industry we have seen that the obvious is constantly overlooked when it comes to trying to solve problems or develop new products and processes. Indeed there is relatively little difference between solving a problem and creating a new product, in both cases you are required to use different thinking from that you would normally use for established products and processes. In essence both scenarios are vindications of Einstein's view. Problems that show as unexpected variations in bakery product quality do occur from time to time. Often considerable time, effort and money are required to identify the causes and solutions concerned. Unexpected quality variations are not the exclusive province of any particular size of manufacturing unit: they can occur in both large and small bakeries. Nor are they exclusive to the production bakery: even the best-controlled test bakery or laboratory can experience unexpected fluctuations in product quality. There is no magic to problem solving. It is normally achieved through critical observation, structured thought processes and access to suitable sources of information. In this chapter we offer a guide to some of the methods that might be employed when trying to solve bakery-related problems. In doing so we must recognise that baking is a complex mixture of ingredient and process interactions so that the solutions to our problems may not always be instant in nature and because ingredients and processes change, new solutions are always being discovered. The complex interactions which underpin baking dictate that there are seldom unique solutions to individual problems. In the majority of cases

2

More baking problems solved

individual quality defects are overcome by changing a number of ingredient and process factors, some of which will be apparently unrelated, though careful study will often reveal that relationships do exist even where they are masked by more prominent effects.

1.1

How to problem solve

Successful problem solving usually requires a methodical approach. It is perfectly possible to stumble quickly on the required solution by chance but more often than not a haphazard approach to problem solving is wasteful of time, resources and money. In addition, stumbling on the solution by chance often means that the root cause of the problem remains unidentified and the opportunity is lost for the systematic assembly of information which may be valuable for solving similar problems in the future. Not all problems are solved using exactly the same approach but the critical elements of the problem-solving process are largely common. In problem solving we normally move from the problem to the cause and finally to the corrective action. However, we must recognise that on many occasions the manifestation of a particular problem does not necessarily have a unique and identifiable cause and so there may be other intermediate steps to take into account in determining the real cause of the problem. This situation can be described schematically as follows: Problem ! primary cause ! contributing factors ! corrective action Or in more simple terms as: What is seen ! why ! because of ... ! corrective action The basic process becomes apparent if we consider two examples of problems in bread making; the first, low bread volume, and the second, collapse of the sides of an open top pan loaf, often referred to as `keyholing' (BPS, pp. 57±8). Low bread volume Externally we observe that the bread is smaller than we expect and this may also have led to a paler crust colour because of the poorer heat transfer to the dough surface during baking. Internally the cell structure may be more open than usual. Since bread volume is a consequence of expansion of the dough by carbon dioxide gas from yeast fermentation and the retention of that gas within the dough matrix (Cauvain, 2007a), there are two potential primary causes of this problem ± lack of gas production and lack of gas retention. To separate the two we will need more observations, and an important one will be whether the rate of expansion of the dough in the prover and oven was normal or slower than usual. If the latter was the case then the primary cause of the problem is likely to

Problem solving: a guide

3

be lack of gas production, and potential contributing factors may include the following: · · · · · · ·

yeast activity or level too low; lack of yeast substrate (food); dough temperature too low; proving temperature too low; proving time too short; salt level too high; proving temperature/time/yeast combination incorrect.

On the other hand, if the proving had been at a normal rate and there was a lack of oven spring, then this would lead us to recognise that the problem would be lack of gas retention. In this case the list of potential reasons for the problem includes: · improver level too low; · incorrect improver formulation; · combination of improver and flour too weak for the breadmaking process being used; · enzymic activity too low; · energy input during mixing too low; · mixing time too short; · dough temperature too low. Note that the `dough temperature' too low appears in both lists because of its effect on yeast activity and the effectiveness of the functional ingredients in the improver, especially if ascorbic acid is used. Keyholing (BPS, pp. 57±8) Externally we observe there is a loss of bread shape but only at the sides of the product. Internally we may see the formation of dark-coloured, dense seams, often referred to as cores. The centre crumb may be more open than we normally expect for the product concerned. Why has this happened? Clearly we have no problems with gas production, since there is no evidence for slow proving and the bread had good volume. We have clearly retained the carbon dioxide gas produced, otherwise the bread would have low volume as described above. In this case the over-expansion of the crumb in the centre of the loaf leads us to the view that in fact the gas retention is excessive. Thus, the primary cause of the problem is excessive gas retention arising from a number of potential individual causes or combinations. The contributing factors may include: · improver level too high; · incorrect improver formulation; · combination of improver and flour too strong for process;

4


· enzymic activity too high; · energy input during mixing too high; · mixing time too long. From the foregoing examples we can see that observation and reasoning are key elements in problem solving. The former can be readily systematised, while the latter will rely heavily on the availability of suitable information to use as the basis for comparisons. The potential sources of such information are discussed below. It is interesting to consider the process by which one might set about identifying the particular cause of a problem, such as the keyholing (excessive gas retention) of bread discussed above. The most likely mental process is one associated with probability achieved by matching the pattern of observations with ones previously experienced and remembered. When we recognise a general similarity between observation and stored image, we are likely to explore in more detail the factors most likely to contribute to the pattern we see. One potential analogy for how we problem solve is that of a tree. The main line of observation is via the central trunk with the potential to explore branches at many points. In the case of our bread problem, if we fail to identify the cause of the problem from our first consideration, then we will close down that line of reasoning, go back to the main theme (the trunk) and then set off on another branch of investigation. Our route through the branches of our reasoning or knowledge tree is complex and occasionally we may jump from branch to branch rather than going back to the trunk before continuing our investigation. The length of time that we take to identify the cause and the corrective actions needed varies considerably from occasion to occasion and from individual to individual, and is more likely to be related to our accumulated knowledge and experiences rather than logical reasoning. Our abilities to recognise and match subtle patterns are probably so intuitive that we are seldom aware of them.

1.2

The record

It is common for the manufacture of bakery products to be based on some starting formulation and formal method of processing the ingredients into the finished product. This will require some form of recorded details of the ingredients to use, their quantities, equipment, process settings and timings involved. Consult any standard recipe or book for bakery food preparation and you will find such details recorded for use by others. In almost all modern bakeries a formal production record will be set up for each of the product types and used by the manufacturing operatives to prepare the various items. Invaluable in problem solving is the formal record of what was actually carried out on a particular occasion. While many operatives will keep to the prescribed formulation and processing recipe, small variations about a given value can occur and lack of information of what the actual values were for a


5

given mix makes problem solving more difficult. It is normal for standard production specifications to allow a degree of tolerance for weights and operating conditions. For example, a temperature specification for a cake batter may be stated as 20 2 ëC. However, such a specification allows for replicate batters to be 18 or 22 ëC and a 4 ëC variation coupled with other small changes may have a larger effect of final product quality than normally considered. A formal record of production can encompass many aspects including the following: · Any variations in the source of the raw materials. For example, changes in flour or whole egg batches, or a new supplier of a particular ingredient. · Changes in analytical data, even where these are still within acceptable limits, because the cumulative effect of small changes in a number of individual parameters can have a large effect on final product quality. · The actual quantities of ingredients used compared with the standard values. For example, in breadmaking it is common to adjust the water level added in order to maintain a standard dough rheology for subsequent processing. In other cases deliberate changes from the standard formulation may have been introduced in order to compensate for some process change. For example, in bread dough the yeast level may be adjusted to compensate for a change in prover temperature so that final proving times do not vary. · The processing conditions, such as mixing times, energies, ingredients and batter or dough temperatures. Once again the values may fall within acceptable ranges but can still have a cumulative effect with other small changes in recipe and process parameters. · Process equipment settings which may vary according to òperator preference' or because of variations in other factors. For example, an unavoidably higher laminated paste temperature may result in greater damage to the laminated structure which may require a compensatory adjustment to roll gap settings during sheeting. · Process timings, such as baking or cooling times. · Changes in packaging materials. The record may be simplified by using the standard recipe as a pro forma against which to record variations. Such techniques have been commonly used to record the weights of individual dough pieces coming from the divider (see Fig. 1) and can be readily adapted for any aspect of bakery production. The record may be on paper, by input to suitable computer-based programs or may be gathered and stored automatically. In addition to the recipe and process records it is very important to have a formal record of finished product quality. Once again it will be common to have some form of product specification with appropriate tolerances against which to make an assessment. Such techniques are commonly the province of the Quality Control Department. The degree of detail recorded will vary. For use in problem solving the formal product specification or quality control record may require some adaptation and enlargement since small, but commonly

6


Fig. 1 Example of a divider record sheet.

accepted, variations may hold the vital clue to the cause of a particular problem. In both the quality control and problem-solving contexts relevant data on the finished product may include the following: · Product size based on height or volume. Devices for measuring product dimensions may be used off- or on-line. They may be as simple as using a rule to measure loaf height or measuring product volume by seed displacement in a suitable apparatus (Cauvain, 2007a) or with laser sensors (e.g., TexVol instruments, BVM-L series, www.texvol.com; VolScan Profiler, Stable Micro Systems, www.stablemicrosystems.com). · Shape may be assessed subjectively and compared with an accepted standard. The introduction of image analysis offers new opportunities for recording product shape, even on-line (Dipix Technologies Inc, www.dipix.com). · The external appearance of the product and the recording of any special features that may be present or indeed the absence of expected features, e.g. lack of oven spring in bread. · Surface blemishes, their size and location on the product. · The coloration of all external surfaces. Descriptive techniques, comparison with standard colour charts, e.g. Munsell (no date), or tristimulus instruments (Anderson, 1995) may be used. Deviations from the norm should be clearly noted. · The appearance of the internal structure, if there is one. Most baked products have some form of internal structure that is an intrinsic component of product quality. Assessment of that internal structure may be subjective and describe the size, numbers and distributions of the cells (open spaces) which go to make the internal structure. Cell structures may be unevenly distributed in the product cross-section or form a `pattern' that is characteristic in different products. Deviations from the norm may be noted. Image analysis is now being used for objectively assessing internal cell structures (Whitworth et al., 2005). · The internal colour may be assessed using techniques described above for surface colour. It is worth noting that the presence of a cellular structure has an impact on the perception of colour and so it is often common practice to include some form of visual assessment, e.g. brightness, which is different


7

from the true colour of a product. Some objective image analysis systems offer a measurement of crumb brightness, e.g. C-Cell (www.c-cell.info). · The physical characteristics that contribute to eating quality may be assessed subjectively with ad hoc or trained panels. Alternatively some form of objective test designed to mimic aspects of sensory analysis may be employed, e.g. texture profile analysis (Cauvain, 1991), squeeze and puncture tests (Cauvain and Young, 2006). · Product odour and flavour may be assessed subjectively on an ad hoc basis or with trained panels. The development of the so-called èlectronic nose' may offer a more objective measure but has yet to approach human sensitivity. Whatever details are considered to be appropriate for the record, it is important to have a standardised format for recording the details. This usually takes the form of a standardised record sheet, paper or electronic, with blank spaces in which to enter the appropriate data or comments. Where a product attribute cannot be measured, an attribute `scoring' system might be used to provide a more objective basis for analysis of the problem. Any number of scoring systems may be employed. One example is given in Fig. 2 and others are given in the literature (e.g., Kulp, 1991; Bent, 1997a; Cauvain and Young, 2006).

Fig. 2 Example of product scoring sheet.

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1.3


The analysis

If a standard record sheet is available then the initial analysis can be as simple as considering whether the recorded data deviate from the process specification and in what direction. The effects of any changes can then be compared with existing knowledge bases (in whatever form) in order to provide the basis of a diagnosis. Sadly few bakery problems are solved with such a simplistic approach. Almost all bakery processes include an element of elapsed time, e.g. proving, baking and lamination, which must be taken into account when analysing the causes of problems. Many larger bakery operations involve continuous production, even though they are batch fed and this adds a further complication to take into account in the analysis. An example from our own experience is that of a plant manufacturing baked puff pastry shells, where deviations in the product dimensions were identified at the end of the baking process. In this instance the plant had to run continuously in order to be efficient and not compromise product quality (i.e., no gaps in the pastry sheet or the oven). The operation was batch fed from the mixer so that the relationship between a given mix batch and the product leaving the oven had to be established first. When this was done it then became possible to identify the contribution that any variation in the mix batch contributed to the problem. After establishing this relationship it became clear that batch to batch variation was not the prime cause of the problem observed, since simple plots of dough properties ex mixer (e.g., temperature or rheology) did not correlate with variations in product quality even when the elapsed time element had been taken into account. The solution to this particular problem lay in a plot of changes in product character with time (see Fig. 3), which upon analysis showed that the variation was more regular than first thought. At first glance it appeared to be the well-known `shift change effect' and to some extent that was true: not, in this case, because of the operator effect on process settings but because each new shift started with a new batch of re-work to add to the virgin paste. As the re-

Fig. 3 Effect of re-work on lift in laminated products.


9

work aged, the effects on baked product character diminished. In this example a simple trend analysis provided the basis for the solution of the problem. One analysis technique that has started to be applied to cereal science and technology is `root cause analysis' (Stauffer, 2000). Not all bakery problems are likely to be potential subjects for this type of analysis, since a key element in this technique is the brainstorming session. Brainstorming usually implies that more than one person is involved and all too often many of us confront bakery problems alone or against a timescale that is insufficient to gather together the necessary team of experts. In manufacturing processes based on batch production, stopping the line until the problem is solved is an option; however, for many bakery processes anything other than a short-term stoppage is seldom an option. However, if the problem is a persistent one or of a catastrophic nature then root cause analysis can be a suitable technique to apply. The role of a team in employing root cause analysis is invaluable in solving intractable problems or making changes to product quality. In the latter case the technique would be to treat the required change as though it were a problem; e.g., if I want greater volume in a cake, then by diagnosing the cause of excess volume, I may well obtain clues as to how to increase cake volume.

1.4

Modelling techniques

The application of statistical methods of analysis is common in many areas of food manufacture. They can be used in problem solving and quality optimisation, though in the manufacturing environment modelling methods often tend to be confined to the plotting of trends using simple graphs as discussed in the example above for a laminated product. More sophisticated statistical and modelling techniques can play their part in helping to build up the information base on what the critical ingredient and process factors are which determine changes in product quality. Once identified, these critical factors can be logged and matched with problems when they occur. To develop such predictive models it will be necessary to carry out experiments in the test bakery or trials on the plant. While trials on the plant are preferred, they can be wasteful of raw materials, energy and time so that the most common practice is to carry out evaluations in the test bakery and `translate' the results to the plant. It is very important to establish any clear changes that are relevant when translating test bakery results to a plant environment. A simple example encountered by the authors was the development of a sponge cake recipe in a test bakery using a planetary-style mixer, while the plant used a continuous mixer to prepare the same recipe batter. In this case it is necessary to remember that less carbon dioxide gas will be lost during continuous mixing than with a planetary mixer so that baking powder levels should be adjusted downwards to compensate for this difference. A typical adjustment would be to reduce the baking powder level for a continuous mixer to be about 75% of that used on a planetary mixer in order to

10


achieve the same sponge cake volume in both the test bakery and on the plant (Cauvain and Cyster, 1996). There are a number of examples of modelling techniques that might be applied to bakery products. Street (1991) provides a review of suitable techniques that may be applied to baked products and there are many examples in the scientific and technical literature. The concept behind the development of such mathematical models is that a relatively limited number of experiments may be used to build models that can be used to predict changes in bakery product quality as a consequence of changes in combinations of ingredients and processes. Once a predictive model has been established then the information can be used for problem solving. For example, suppose that we show by experimentation how loaf volume varies as a result of an interaction between the level of ascorbic acid in the dough and mixing time. At some later stage we may encounter a problem with low bread volume and then we would be able to use the output from our model to help decide whether the problem was associated with the level of added ascorbic acid or mixing time, or both. Furthermore we might use our model to show which changes were most likely to restore our bread volume to its original level. Baking is a complex food process with many ingredient and process interactions. These interactions lead to complicated models that are often difficult to apply. For example, for a given set of mixing conditions we would observe that bread volume increases with increasing levels of ascorbic acid reaching a maximum and thereafter there will be little change in volume for increasing additions of ascorbic acid. This occurs because the oxidation effect of ascorbic acid is limited by the availability of oxygen from the air incorporated during dough mixing (Cauvain, 2007b). The availability of oxygen is affected by yeast activity, so that yeast level becomes an influencing factor. Both yeast and ascorbic acid activity are temperature sensitive and proceed at a greater rate when the temperature increases. Dough temperature is a function in part of ingredient temperatures and in part the energy imparted to the dough during mixing. Energy transfer in turn is related to the mixing time. So, too, is gas occlusion to a lesser degree, because during mixing an equilibrium point is reached when the entrainment process is balanced by the disentrainment process. This equilibrium may occur before the end of the mixing time. So, for the example given above, while we set out to study the effects of the level of ascorbic acid and mixing time, we must also ensure that we measure: · · · ·

ingredient temperatures; final dough temperature; gas occlusion in the dough; energy transferred to the dough.

These records are necessary because we cannot independently control some of the properties concerned, e.g., mixing time, energy and dough temperature. Whenever we do work during mixing we must expect there to be a temperature rise. This relationship also holds true if a water or other coolant jacket has been


11

fitted to the mixer and in this case we must remember that the coolant temperature in the jacket will also rise by the time that it leaves the jacket. There tends to be greater variability in product quality for products manufactured on a plant than one sees in many test bakery environments. This process `noise' in the data can mask some of the critical issues that control product quality and therefore weaken the value of any models that have been developed. There are a number of statistical techniques that can be used to help separate such noise from underlying effects, trends and relationships. In many manufacturing processes the specified product characteristics can be achieved by many different combinations of formulation and process conditions. Taguchi methods use experiments to search systematically and efficiently for combinations of `control' factors that minimise product variability in the face of variations in `noise factors' such as ambient temperature. Taguchi methodology has been applied to the manufacture of bakery products, in particular in a study of the factors that affect the quality of puff pastry (DTI, 1993). In some cases effective problem solving can be initiated by studying the effects of small perturbations on the plant. A major issue with carrying out trials on the plant is the potential loss of production arising from the manufacture of out-of-specification products. However, there is a distinct advantage to plant trials in that large numbers of samples are being made, which increases the potential for statistical and practical analysis. Most product specifications have a degree of tolerance associated with the final product so that small variations can be accommodated without loss of production.

1.5

Matching patterns and visualising changes

Sometimes when dealing with complex problems it is an advantage to sketch out the salient features with a diagram or create some collage of salient information on a board (like a story board for the creation of a film). A simple example is illustrated in Fig. 4 in which the potential routes for the migration of moisture in composite bakery products are identified, annotated with relevant data on moisture contents and product masses. The drawing of diagrams such as that shown in Fig. 4 helps to ensure that all of the relevant processes are considered before carrying out detailed calculations and investigations. Human beings have a significant capability for being able to match patterns in data and in many ways when we are problem solving we spend a lot of time comparing what we see with the patterns that we all hold in our minds. Subconsciously we look for a pattern of information in a current problem and compare that with previous patterns of events and information to see if they provide clues for solving the current quality problem. There are many different ways of creating patterns. The creation of knowledge trees and knowledge fragments is one example and is discussed in more detail in the following section. The knowledge tree is like a flow diagram similar to that created by engineers to show the movement of raw materials through various stages en

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Fig. 4 Schematic identifying the characteristics of the different components of a composite cake product and the potential routes of moisture migration.

route to becoming a finished product. The same basic principle is used by systems analysts when they are constructing diagrams to show the flow of information, with different symbols representing different types of activity or decisions which need to be made. Cauvain and Young (2006) illustrated possible examples of pattern matching for the baking industry using a series of `spider diagrams' to relate certain characteristics of wheat with those of the subsequent flour, dough and bread. As well as providing a relatively simple means of developing patterns relating raw materials and finished products, the process of deciding which characteristics to include in the various diagrams is an important first step in understanding the cause of quality problems. When it comes to identifying the key roles of different ingredients and processes in determining a particular aspect of final product quality, it is useful to be able to identify the relative importance of the individual changes. It may be possible through mathematical modelling to identify the relative importance of the effect of different ingredients, recipes and processes or process changes but it can sometimes be sufficient in problem solving to use a simple diagram to understand the different contributions (Cauvain and Young, 2006). An example of this type of approach is given in Fig. 5, which examines the impact of some process and ingredient factors on the hardness and crumbliness of cookies. The development of a gluten network in cookie dough is not usually considered to be desirable but if this should happen, e.g. through over-mixing, the resultant product will be harder eating. As the sugar level in a cookie formulation increases, the resultant product gradually loses its initial crumbliness and becomes harder (e.g. as seen with ginger nuts), while increasing additions of fat give increasingly crumbliness as the fat interferes with the development of the gluten structure. The angle at which the individual vectors proceed from the


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Fig. 5 The impact of some process and ingredient factors on the hardness and crumbliness of cookies.

origin gives an indication of the relative impact of any changes, so that this relatively simple diagram can provide a first indication of the potential interactions taking place in a particular baking environment. For example from Fig. 5, if we wish to reduce the fat level in a cookie formulation but do not wish to end up with a harder biscuit then we would consider a reduction in gluten development by adjusting mixing conditions or methods or changing ingredients, such as flour type, which contribute to gluten formation.

1.6

The information sources

Not many of the problems that we may encounter in the manufacture of bakery products are likely to be so unusual that they have not been encountered and recorded before. Even where an apparently new problem arises, access to suitable information sources often reveals a problem and solution so similar that it can be readily adapted to our particular needs. For example, most of the problems that we are likely to encounter in the production of cakes with heattreated cakeflours (BPS, pp. 30±1) will have similar solutions to those that would apply if we were using chlorinated cakeflours (BPS, pp. 32±3). Even though it may be the first time that we have used a heat-treated flour, we therefore have a suitable base for identifying the solution to our problem. The availability of suitable information is a fundamental tool for our ability to problem solve successfully. Traditionally such information sources could be classified as personal and written. More recently computer-based sources have become increasingly available sometimes as databases but in other cases in forms that would not be classified as an electronic equivalent of the written word.

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Personal Even in today's fast-moving electronic age there is no substitute for personal experience which builds one's own portable information source. However, few of us will spend long enough in positions that allow the systematic build-up of the appropriate knowledge through `trial and error' studies. Aspects of problem solving may be taught in our years of academic study but these are seldom detailed enough to provide us with the comprehensive information base required. Personal contacts with experts and consultants can be used to supplement the individual information base. Contact with other professional bakers and professional baking organisations are invaluable because it allows access to a wider range of experiences. Thus membership of professional bodies such as the British Society of Baking, the American Society of Baking and the Australian Society of Baking, which are linked with one another, has benefits in developing one's own knowledge base. Attendance at suitable conferences, technical meetings, workshops and short courses can provide relevant information. Written The scientific and technical literature provides the most obvious source for written material which aids in problem solving. Starting a collection of ùseful' articles and some form of index is very helpful in establishing your own information base. Included in the written form are pictorial libraries of faults and associated text related to their identified causes. Such libraries may be built for oneself or may be purchased from a suitable source. Over the years many of the `rules' related to problem solving in baking have been summarised and published (e.g. Street, 1991; Bent, 1997b). These generally take the form of lists of faults and associated causes. In many ways such rules are of limited value because they seldom consider or assign a likelihood value and so a personal degree of judgement as to which of the causes to investigate first is required. Such lists tend to deal only with the more common problems and seldom consider interactions between ingredients or ingredients and processing. Also the causes of faults are given equal weighting; thus there is no expression as to whether a particular cause is more likely than another. The values of a personal record can be significantly increased by systemising the knowledge record. A series of checklists can be constructed to identify contributions of ingredients and processes to final products and their appropriate intermediates (e.g., dough, batter, paste). An example of such an approach is illustrated for pastry in Tables 1±3. Checklists may be populated with the type of information identified in Section 1.7. A `first level' checklist (Table 1) identifies the ingredients that may be used in the manufacture of pastry and considers the potential impact on the various final product characteristics. Filling in this first checklist is merely a question of identifying whether a particular ingredient has an effect or not; those that do have an effect could be marked with an `X'. In Table 1 the different quality of


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Table 1 Example of level 1 checklist for recording the potential effects of ingredients and their qualities on paste and pastry characteristics

the flour, fat, and sugar are known to have an effect and so are marked for consideration. Re-work has been included as an ìngredient' because of the profound effect that it has on both the paste and the final product; the re-work quality would be controlled by its age, temperature and length of storage time. Consideration is then given to whether varying the ingredient level will impact on paste characteristics and final product quality. The example illustrated in Table 2 does not include flour, since it is common practice to assess the impact of ingredients with respect to flour at a standard level in the bakery (Cauvain and Young, 2006). At this stage there is no need to consider the direction of impact. The final level 1 checklist considers the impact of the processing steps applied in the manufacture of the bakery product concerned. In Table 3 some examples related to the mixing, processing and baking of pastes are included. Again it is only necessary to identify whether there is an impact or not from a particular process step. The level 1 checklists help focus the subsequent line of reasoning that might be applied in problem solving or product development. The `second level' checklist considers the impact of the level of the different recipe ingredients and process settings. In this case it will be necessary to consider the direction of change for given product characteristics (e.g., larger, smaller) and link these with changes in ingredient level (e.g., higher, lower) or process conditions (e.g., mixing time longer or shorter). Examples of level 2 checklists are illustrated in Tables 4±6 and they show the type and range of information that might be

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Table 2 Example of level 1 checklist for recording the potential effects of ingredient levels of paste and pastry characteristics

Table 3 Example of a level 1 checklist for recording the potential effects of processing conditions on paste and pastry characteristics

Table 4 Example of a level 2 checklist for recording the potential effects of ingredient qualities on paste and pastry characteristics

Table 5

Example of level 2 checklist for recording the potential effects of ingredient levels on paste and pastry characteristics

Table 6

Example of a level 2 checklist for recording the potential effects of processing conditions on paste and pastry characteristics

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included. If an ingredient or process parameter was identified at level 1 then it is carried through to level 2. Entries at level 2 can be directional (as illustrated) or if hard data exist (e.g., from mathematical modelling), these can be entered instead to give the level 2 checklists a more `predictive' capability. Missing from the checklist approach is the ability to directly record complex interactions but they can be a useful first step in assembling the complex knowledge required for solving bakery problems. They can also be useful for gathering and systemising the information required for the development of computer-based knowledge systems (see below). Constructing knowledge trees and knowledge fragments Another approach to recording technical information can take the form of constructing knowledge trees. Usually the construction of the tree starts at the top and works downwards to the `roots'. In practice the information that it holds can be used from the `bottom up' for product development and from the `top down' for product and process quality optimisation. The construction of the knowledge tree starts with the identification of a final product or intermediate property of interest and proceeds by identifying all those factors that contribute to the identified property or characteristic, both individually and collectively. An example of this approach is given in Fig. 6 for lift in laminated puff pastry. Moving from the top of the tree downward we can see that the approach is to progressively break down complex interactions until single contributing factors are identified; these may be considered as the roots of the tree, even if not all of them are `planted in the ground'. Cauvain and Young (2006) provide another example of a knowledge tree for the eating quality of bread and cake products. As complex as these diagrams appear, they only par-

Fig. 6 Part of a knowledge tree identifying the factors that contribute to pastry lift.


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tially address the issues of the complex ingredient±recipe±process interactions which underpin baking. Sometimes it is not possible to develop a full knowledge tree and it is easier to break the structure down into a series of knowledge fragments. This is a technique that we have pioneered and used in many situations. An example of a knowledge fragment is illustrated in Fig. 7 and is one relevant to ascorbic acid oxidation in breads made using the Chorleywood Bread Process. The fragment identifies a number of the key interactions that take place in mixing and how they relate to the qualities of the final product. Fragments are visual aids that help you to quickly see relationships between pieces of knowledge. They can express or define information and knowledge about an ingredient, a term used in baking or a processing step or about any information you may wish to structure so that it is easy to use again, either as an aide-meÂmoire or to help in your understanding of a topic. They are constructed in a similar way to a `flow diagram'. The items of knowledge can be linked together using lines and arrows. They need to be structured and classified in a simple way and saved so that they can be retrieved easily when needed. They might be considered as a `diagrammatic knowledge-/data-base'. The key terms used in them can be indexed so that retrieval is easy. If faults or quality defects are shown in the fragments, they can be used to identify the questions that need to be asked to determine a solution to a baking problem or quality defect. They can help you to link all the technical information that you acquire about baking. In the example provided, Oxidation in CBP, all of the relevant knowledge about oxidation is illustrated. The mechanism by which ascorbic acid takes part in oxidation, the links to mixing and energy requirements, and possible processing issues are shown. Its contribution to gas retention is flagged. The result of underor over-oxidation for the product being considered, in this case generic plant bread, can be inserted. By referencing some of the key terms used in the fragments, e.g. gas retention, gas production, fault ± low volume, fault ± coarse structure, etc., the relevant fragments can be identified and examined when a product exhibits a particular fault, e.g. coarse structure. Any fragments showing this fault can be used in the trail to find the cause of the fault and its correction. Such knowledge fragments can have considerable value in their own right as they provide detailed information focused on one or two aspects of a larger and more complex structure. Knowledge (computer)-based systems Computing technology offers a special opportunity to help with problem solving, quality optimisation and product development. In particular, reasonbased programs, commonly known as èxpert systems', can be used in fault diagnosis and linked with corrective action. The Flour Milling and Baking Research Association at Chorleywood was the pioneer in applying such technology to the baking industry. Later the work was continued in the Campden and Chorleywood Food Research Association.

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Fig. 7 Example of a knowledge fragment related to ascorbic acid oxidation in the Chorleywood Bread Process (ß Baketran 2008).


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Expert, or knowledge-based systems as they are now commonly referred to, can combine facts and rules to solve problems. The `rules' can take several forms including mathematical models, `rules of thumb' and ìntuitive' rules. The latter may well take the form of ìf I increase the level of ingredient X then property Y in the product will change in a positive direction' (cf. the checklist approach discussed above). Such rules may not quantify the degree of change, only the direction. Knowledge-based systems can contain many rules that should be capable of validation. They should not contain opinion but rather concentrate on facts. Such systems can perform a fault diagnosis within a few minutes and are capable of considering large information bases very quickly. They can consider many interactions and are often written to provide degrees of likelihood in the answers so that the process of identifying corrective actions and assigning priorities is more readily possible. Images and text can be integrated and displayed to provide pictorial display of product characteristics. In some cases it may be possible to diagnose faults with a knowledge-based system based solely on images run using touch-screen computing technology (Young, 1998a). Unlike humans, knowledge-based systems never forget and always consider all the necessary information. However, they are not perfect because they rely on human programming and so are only as good as the information they contain. Nevertheless, they can play an important role in aiding problem solving, quality optimisation and product development (through `what if?' questioning) and offer a significant advantage over the classical written fault diagnosis text lists. Knowledge-based systems have been applied for problem solving in the production of bread (Young, 1998a), cake (Petryszak et al., 1995; Young et al., 1998) and biscuits. In addition to their application for problem solving, they may be used in product development (Young, 1997), process optimisation, e.g. retarding (Young and Cauvain, 1994; Young, 1998b), and for training (Young, 1998a). The `Web' The development of the World Wide Web has increased the range of options available for information and contacts to help with problem solving. There are many sites that can be accessed for providing information but it is important to try to ensure that the information received has some validity and credibility. It is therefore best to deal with reputable and well-known sources. Developments in web-based technologies will considerably increase the availability of computer-based tools such as knowledge-based systems. Work has been undertaken to provide access to such programs on an on-line basis, linked with the transfer of appropriate baking technology (Young, 1999) but such approaches have yet to achieve their full potential in baking and allied industries. A number of professional bodies associated with baking offer their problemsolving services via web-based systems. There are also commercial organisations who offer assistance with problem solving, commonly on a fee-

24


paying basis. Details of their services can be obtained from their relevant web sites.

1.7

New product development

Much of the information and advice that has been given so far in this chapter is related to problem solving. However, there are significant similarities between the processes involved in problem solving and in developing new bakery products. For example, it is common practice, before undertaking a new development, to consider the properties that are sought in the new product and compare them with existing product qualities. If the quality differences between the new product and the existing product are treated as though they are quality deficiencies, then the information and techniques which are commonly used in problem solving are now equally applicable to new product development. In this process the question is not `How do I solve this problem?', rather it is `How do I move the product quality in a given direction?'. Knowledge fragments and knowledge trees can have significant roles to play in new product development because they will contain the information which allows the product developer to make informed decisions as to which ingredient, recipe or process changes to make in order to manipulate product quality and should also contain some identification of the key product interactions. When new products are developed, the techniques described above should assist in moving the quality of the concept product under development smoothly to the finished product ready for launch in the marketplace. However, occasionally it can be forgotten that there needs to be a structure to the product development process itself. In the worst cases the point can be reached where a great deal of money is expended without achieving a robust sustainable product. The list below can be used as a guide to successful product development. It is not exhaustive and can be augmented for local circumstances. At each major stage it is advisable to consider a `Go/No go' decision for the product so that it is developed on a sound commercial and technological basis. Concept Discussion about product feasibility with · Marketing · R and D · Engineering · Quality control · Production · Procurement. Consumer research required? · Market studies · Trend analysis


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· Product positioning · Focus group testing. Defining the product · Characteristics · Specifications · Eating quality · Appearance/dimensions, etc. · Shelf-life requirements ± both organoleptic and mould-free · Formulation · Engineering requirements/equipment · Any legislation issues · Nutritional issues · In-house capability · Preliminary product costings/commercial viability of product · Consumer acceptance · Budget investigation · Project manager and team ± propose · Criteria for success ± define o Can the product be made easily and efficiently? o Can it be sold for the right price and make a profit? Go/No go decision point Product development investigation ± prototype product · Budget · Define timeline for the prototype product development · Define areas of responsibility · Formulation development for constituents of product, e.g. biscuit, cream, filling, coating · Flavour profile development · Ingredient assessments · Lab pilot-scale development of the product (including tasting) · Records of development of prototype, including photographs · Investigation of needs for processing equipment, e.g. have we got suitable equipment, can we buy it off the shelf, is it a one-off? · In-house expertise for product development and production · Consultants/specialist input required? · Training required? · Consumer acceptance trials? · Assessment of lab pilot-scale products · Quality analysis o shelf-life o stability

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o rheological properties o organoleptic properties o flavour profiling o other analytical tests required? · Potential market ± route · Costings for the product · Criteria for success ± revisit. Go/No go decision point Scale-up to commercialisation assessment · Budget · Timeline · Process development for large-scale production · Engineering work required ± equipment development/modification · Increasing production or baking capacity? · Manufacturing and baking specifications · Risk assessments · Packaging development/integrity testing/shelf-life issues. Prototype trials on the plant · Budget · Timeline · Ingredient procurement and assessment · Equipment ± purchase/recommendations, set-up, liaison with production schedule, skills required, personnel training, expertise to be brought in · Keeping/shelf-life trials · Consumer trials · Marketing input. Go/No go decision point Pre-launch trials · Specification and procurement of ingredients · Purchase of equipment if required · Marketing input · Packaging design · Tasting trials with consumers · Labelling · Quality control requirements · Plant/housekeeping/production team · Assessment of production product · Shelf-life trials continued. Go/No go decision point


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Launch · Marketing · Advertising · Packaging · Pricing · Procurement · Hand over to production team as a portfolio product · Set up quality assessment. On-going product maintenance/handover · Confirmation of product specification definition, e.g. archive of recipe and ingredient specifications, processing details, etc. · Quality control specifications and reports · Scheduling considerations · Consumer acceptance · Crisis management plan for potential disaster/mishaps, e.g. change of ingredient, change in legislation, plant breakdowns · Marketing plans · Keeping trials.

1.8 Some key ingredient and process factors affecting product quality The following lists identify examples of the primary factors to consider when looking at quality problems with some of the different groups of bakery products and provide summaries of some of the key ingredient and process (secondary) factors which affect product qualities. The lists are not comprehensive but may provide a useful guide to establishing the reader's own database, a series of personalised checklists or knowledge fragment and knowledge trees. Bread Primary factors · Cell creation · Gas production · Gas retention · Dough development · Dough rheology. Volume · flour protein quantity; · flour grade colour or ash; · improver level ± oxidants, emulsifiers, fats, enzyme-active materials; · improver composition ± oxidants, emulsifiers, fats, enzyme-active materials;

28 · · · · ·

More baking problems solved yeast level; dough development ± energy/time; dough temperature; prover conditions ± time/temperature/humidity; oven conditions ± temperature.

Crust colour · sugar levels; · improver level; · improver type; · dough enzymic activity; · fermentation conditions ± time/temperature/yeast level. Crumb cell structure · flour properties ± protein quantity; · improver level ± oxidants, emulsifiers, fats, enzyme-active materials; · improver composition ± oxidants, emulsifiers, fats, enzyme-active materials; · yeast level; · dough development ± energy/time; · dough temperature; · dough moulding. Crumb colour · flour grade colour/ash/bran level; · crumb cell structure; · dough moulding. Crumb softness · volume; · cell structure; · ingredients ± emulsifiers, enzyme-active materials; · moisture content; · baking conditions ± time; · storage conditions ± temperature/time. Cakes and sponges Primary factors · Cell creation · Gas production · Batter viscosity. Volume · recipe balance; · baking powder level;

Problem solving: a guide · emulsifier level; · mechanical aeration; · baking temperature. Crust colour · recipe balance ± sugars, milk products; · baking ± conditions temperature. Crumb cell structure · mixing time; · mechanical aeration; · recipe balance; · baking powder level. Crumb colour · Ingredients, e.g. egg level. Crumb softness · volume; · moisture content; · cell structure; · baking time; · storage conditions ± time/temperature. Pastries Primary factors · Paste rheology. Shape · recipe balance; · mixing conditions ± time/energy; · process conditions ± resting periods. Fragility · recipe balance; · mixing conditions. Eating qualities · recipe balance; · moisture content; · moisture migration; · storage conditions ± time/temperature.

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Laminated products Primary factors · Gas production · Gas retention · Dough development · Paste rheology. Shape · recipe balance ± fat level; · mixing conditions ± time/energy; · process conditions ± resting periods; · lamination conditions ± numbers of layers, temperature. Lift · recipe balance ± fat level and type; · mixing conditions ± time/energy; · production method ± English/French/Scotch; · process conditions ± temperature, resting periods. Eating qualities · recipe balance ± fat level; · fat type; · moisture content; · moisture migration.

1.9 Conclusions Many of us will be faced with the need to solve problems associated with baked products, whether we work in a bakery or the industries which supply it. Some will be minor and some extensive in nature, but they will all be important. To a large extent identification of the causes of the problem will be based on sound observation and the application of appropriate knowledge in a systematic manner. As bakers we have to deal with a mixture of complex ingredients and their many interactions with one another and the production processes we use. For practical bakers many of the causes of problems are `hidden'; for example, a change in flour properties is seldom obvious until a defective product leaves the oven. There is always a need to find the `quick' solution and traditionally this was based on training and experience. Today's bakers seem to get little of the former and are seldom given the time to obtain the latter. Modern information technologies can go some considerable way in providing suitable problem-solving tools for the modern baker. However, there is no single unique source that can provide all of the necessary solutions to baking problems but keen observation, a methodical approach and good information sources will almost always help identify cause and solution.


1.10

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References

(1995) Crust colour assessment of bakery products. AIB Technical Bulletin XVIII, Issue 3, March. BENT, A.J. (1997a) Confectionery test baking, in The Technology of Cakemaking, 6th edn. (ed. A. J. Bent), Blackie Academic & Professional, London, UK, pp. 358±385. BENT, A.J. (1997b) Cakemaking processes, in The Technology of Cakemaking, 6th edn. (ed. A. J. Bent), Blackie Academic Professional, London, UK, pp. 251±274. CAUVAIN, S.P. (1991) Evaluating the texture of baked products. South African Journal of Food Science & Nutrition, 3, November, 81±86. CAUVAIN, S.P. (2007a) Bread ± the product, in Technology of Breadmaking, 2nd edn. (eds S.P. Cauvain and L.S. Young), Springer Science+Business Media, New York, USA, pp. 1±20. CAUVAIN, S.P. (2007b) Breadmaking processes, in Technology of Breadmaking, 2nd edn. (eds S.P. Cauvain and L.S. Young), Springer Science+Business Media, New York, USA, pp. 21±50. CAUVAIN, S. P. and CYSTER, J.A. (1996) Sponge cake technology. CCFRA Review No. 2, CCFRA, Chipping Campden, UK. CAUVAIN, S.P. and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2006) Baked Products: Science, Technology and Practice, Blackwell Publishing, Oxford, UK. DTI (1993) Quality Optimisation in the Food Industry ± Applying Taguchi Methods in the Baking Industry, DTI Project CSA 1923, DTI, London, UK. KULP, K. (1991) Breads and yeast-leavened bakery food, in Handbook of Cereal Science and Technology (eds K.J. Lorenz and K. Kulp), Marcel Dekker, New York, USA, pp. 639±682. MUNSELL, A.H. (no date) Munsell System of Colour Notation, Macbeth, Baltimore, USA. PETRYSZAK, R., YOUNG, L.S. and CAUVAIN, S.P. (1995) Improving cake product quality, in Proceedings of Expert Systems 95, the 15th Annual Conference of the British Computer Society Specialist Group on Expert Systems, December, pp. 161±168. STAUFFER, J.E. (2000) Root cause analysis. Cereal Foods World, 45, July, 320± 321. STREET, C.A. (1991) Flour Confectionery Manufacture, Blackie Academic & Professional, London, UK. WHITWORTH, M., CAUVAIN, S.P. and CLIFFE, D. (2005) Measurement of bread cell structure by image analysis. In Using Cereal Science and Technology for the Benefit of Consumers (eds S.P. Cauvain, S.E. Salmon and L.S. Young), Woodhead Publishing Ltd, Cambridge, UK. YOUNG, L.S. (1997) Water activity in flour confectionery product development, in The Technology of Cakemaking, 6th edn. (ed. A.J. Bent), Blackie Academic & Professional, London, UK, pp. 386±397. YOUNG, L.S. (1998a) Baking by computer ± passing on the knowledge, in Proceedings of the 45th Technology Conference of the Biscuit, Cake, Chocolate and Confectionery Alliance, London, pp. 63±67. YOUNG, L.S. (1998b) Application of knowledge-based systems, in Technology of Breadmaking (eds S.P. Cauvain and L.S. Young), Blackie Academic & Professional, London, UK, pp. 180±196. YOUNG, L.S. (1999) Education and training for the future, in Proceedings of the 86th Conference of the British Society of Baking, British Society of Baking, pp. 13±16. ANDERSON, J.

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YOUNG, L.S. and CAUVAIN, S.P. (1994)

Advising the baker, in Proceedings of Expert Systems 94, the 14th Annual Conference of the British Computer Society Specialist Group on Expert Systems, December, pp. 21±33. YOUNG, L.S., DAVIES, P.R. and CAUVAIN, S.P. (1998) Cakes ± getting the right balance, in Applications and Innovations in Expert Systems VI, Proceedings of the 18th Annual Conference of the British Computer Society Specialist Group on Expert Systems (ed. A. Mackintosh) Cambridge, December, SGES Publications, Cambridge, UK, pp. 42±55.

2 Flours and grains

2.1 We have seen references to the ash content with white flours but this is not a figure that appears on the specification from our UK miller. Can you explain what the ash content means and should we ask for it to be determined on our flours? The ash test is based on the incineration of a known weight of a flour sample at 900ëC in a suitable furnace; the material that remains after incineration comprises the inorganic minerals and is referred to as the ash (ICC, 2005). There are alternative testing methods that use a lower temperature for heating the sample, e.g. the AACC method for ash determination uses a temperature of only 600ëC (AACC, 2008). Whatever the testing method that is applied the aim remains the same. The minerals in cereal grains are concentrated in the outer bran layers which surround the inner endosperm. Thus, as a general principle the higher the ash content of a `white' flour, the greater the proportion of bran which can be present in the sample. The complex geometry of the wheat grain and the physical properties of the materials concerned means that the bran skins cannot be `pealed' from the endosperm like layers on an onion and, even in the most efficient of flour mills, it is inevitable that some fragments of the outer bran layers will find their way into the white flour which essentially comes from the endosperm. The ash test may therefore be seen as an indicator of the `purity' of white flour in that the more of the bran which is incorporated with the wheat endosperm, the higher the ash level will be. It follows that since wholemeal flours are 100% of the grain, then the ash content will be considerably higher than that of white flours. In the UK (and elsewhere) there is a statutory requirement for white flours to be fortified with calcium carbonate at levels between 235 and 390 mg/100 g (The

34


Bread and Flour Regulations, 1999) before the flour leaves the mill. This requirement is related to the nutritional status of flour. Calcium carbonate is an inorganic substance which remains as part of the ash residue on testing. However, unlike bran it has no technological impact in baking. Since calcium carbonate would measure as ash, using the test for UK flours will yield a higher value and distort the application of the information for bakery purposes. In light of the above scenario UK millers do not routinely use the ash test to monitor final flour quality, instead they use a test commonly referred to as the `grade colour figure' (see 2.2). This test, carried out with a `Colour-grader' with a specified light source (Cauvain, 2009), is based on the assumption that higher levels of bran will yield a darker flour colour. There is a broad agreement between ash and grade colour figure (see Fig. 8) but one value cannot be used to predict the other with any degree of certainty. This is because the distribution of minerals is not uniform throughout the wheat bran layers and the particle size of the bran also distorts the relationship. While neither test can be used to predict the results of the other, both have relevance to the breadmaking potential of a given white flour. In its simplest form the higher the ash value or grade colour figure, the poorer the gas retention capacity of the flour in breadmaking. This, in turn, means that loaf volume will fall if the ash or grade colour figure increases. Cauvain (2009) provides relevant ash data for a range of mill fractions included in an example of a straight run white flour. In broad terms the ash level has been equated with the èxtraction rate' of flours (i.e., the proportion of the original grain turned into flour). Kent and Evers (1994) published data relating milling extraction rate to ash values and showed that an increase in extraction rate from 70 to 85% increased the measured ash level in the flour from 0.44 to 0.92%. However, ash levels should not be taken as an absolute indicator of extraction rate because, as noted above, as the minerals in the wheat grain are not uniformly distributed in the grain components and so the milling techniques that may be used can skew the data. References

(2008) Approved Methods 10th edn., AACC International, St. Paul, MN. (2009) Applications in the flour mill. In (eds. S.P. Cauvain and L.S. Young) The ICC Handbook of Cereals, Flour, Dough & Product Testing: Methods and Applications, DEStech Publishing, Lancaster, PA, pp. 91±124. ICC ± INTERNTATIONAL ASSOCIATION FOR CEREAL SCIENCE & TECHNOLOGY (2005) Determination of ash in cereals and cereal products, ICC Standard Method 104/ 1, Vienna, Austria. KENT, N.L. and EVERS, A.D. (1994) Technology of Cereals, 4th edn., Elsevier Science Ltd, Oxford, UK. THE BREAD AND FLOUR REGULATIONS (1999) SI 1999, No. 1136 ± SI 1998, No. 141, HMSO, London, UK. AACC

CAUVAIN, S.P.

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2.2 What does the term grade colour figure mean in flour specifications? How is it measured? What are the implications for bread quality? Grade colour figure (GCF) (sometimes written as Colour Grade Figure or Flour Colour Grade) is a measure of flour colour. The technique uses light reflectance at a specific wavelength from a flour-water paste held in a glass cell. It was developed by Kent-Jones and Martin (1950) and refined by Kent-Jones, Amos and Martin (1950). The `Colour Grader' has undergone a number changes to improve its reliability and sensitivity. In many countries GCF is an accepted method for the evaluation of mill performance and flour quality. While generally accepted as a measure of the level of bran present in white flours, it is appreciated that GCF is affected by a number of other factors, including the intrinsic colour of the wheat endosperm (Barnes, 1986) and the impact of any bleaching processes which may be carried out (bleaching white flours is seldom practised in modern mills). In the UK the mandatory addition of chalk to white flour means that the measurement of ash as a predictor of the breadmaking potential of the flour was misleading because the measured ash value was raised by the addition of the chalk (see 2.1). Thus GCF came to be used more readily as an indicator of the level of bran `contamination' in white flour. The form of wheat grains, especially the crease, means that it is difficult to completely separate the bran layers from the starchy endosperm and it is inevitable that small particles of bran `powder' find their way into white flour. The bran particles have the same size as the endosperm fragments and so cannot readily be separated by sieving. The level of bran particles may be reduced through aspiration (in purifiers) since they are less dense than the endosperm fragments but complete separation is seldom achieved. In general, the higher the GCF value, the higher the level of bran present in a given white flour, the poorer the gas retention properties in bread dough and the darker the bread crumb colour. This statement does not convey the complete picture for white flours, which are a composite of many different `white' machine flours obtained during wheat milling. The level of bran varies in each of these flours according to the layout and operation of the mill. Cauvain et al. (1983) provided examples of the variation in GCF amongst machine flours with relevant bread volume data. There is a general relationship between the two measured flours properties (see Fig. 8) but GCF cannot be accurately used to predict flour ash and vice versa. It should be noted that when the GCF test was developed it was intended to be used with white flours and so measurements on brown or wholemeal have limited relevance. Machine flours that are high in bran content (i.e. high ash or high GCF) may often be referred to as `low grade' flours to indicate their relatively poor breadmaking potential. The quantity of such flours produced and present in straight run flour is usually relatively small so the overall impact on flour GCF

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Fig. 8 Relationship between flour ash and grade colour figure.

and loaf volume arising from their addition is limited. Flours that are especially low in bran (i.e., low GCF and low ash) may often be referred to as `patent' or `top patent' flour. Such flours have good breadmaking potential even though their protein content may be lower than a straight-run flour. Cauvain et al. (1985) using a range of white commercial flours showed that as a general `rule of thumb' an increase in flour GCF of one unit was equivalent for its negative impact on loaf volume to a decrease in 1% of flour protein for bread made by the Chorleywood Bread Process. The GCF measurement method is not normally used to assess the quality of wholemeal flours; not least because the reliability of the measurements can be affected by the size on the bran particles which are present in the flour. In white flours the bran particles will be no bigger than the largest of the wheat endosperm fragments which are present. References

(1986) The influence of wheat endosperm on flour colour grade. Journal of Cereal Science, 4, 143±155. CAUVAIN, S.P., CHAMBERLAIN, N., COLLINS, T.H. and DAVIES, J.A. (1983) The distribution of dietary fibre and baking quality among mill fractions of CBP bread flour. FMBRA Report No. 105, Campden-BRI, Chipping Campden, UK. CAUVAIN, S.P., DAVIES, J.A. and FEARN, T. (1985) Flour characteristics and fungal alphaamylase in the Chorleywood Bread Process, FMBRA Report No. 121, CampdenBRI, Chipping Campden, UK. KENT-JONES, D.W. and MARTIN, W. (1950) A photo-electric method of determining the colour of flour as affected by grade, by measurements of reflective power. Analyst, 75, 127±133. KENT-JONES, D.W., AMOS, A.J. and MARTIN, W. (1950) Experiments in the photo-electric recording of flour grade by measurements of reflective power. Analyst, 75, 133±142. BARNES, P.J.

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2.3 Can you explain the functions of the different components in the wheat grain and, after milling, their contributions to the manufacture of baked products? Shapes vary among the various cereal grains though their main components are surprisingly similar. In the preparation of wheat flour we are dealing with the seed of the plant formed during its growing cycle. The individual seed grains are the next generation of plants and contain all of the nutrients and specialist components to start the growing cycle under appropriate conditions. The individual seed grains are composed of a series of different tissues, each with its own special function in the life cycle of the plant. In broad terms we describe wheat as being composed of a series of outer layers variously referred to as the seed coat or bran skins, an inner endosperm and the embryo. Unfortunately there is confusion in the use of the latter term and in common usage it is often referred to as the germ of the grain. The term germ is most commonly used within a milling context and refers to an embryo-rich fraction of the grain obtained during milling processes. For the seed the functions of the different components are relatively clear; the bran layers enclose and protect the food reserves (the endosperm) for the growth of the future plant while it is from the embryo that the proto roots and shoots will spring when conditions are appropriate. The physical structures and chemical composition of the seeds are far too complex to describe in a book on baking and so the reader is referred elsewhere for such detail (Lorenz and Kulp, 1991). The overall proportions of the three main wheat seed components vary slightly according to the wheat variety and the conditions under which it is grown but the variations are relatively small. To add to the confusion that commonly surrounds the different components of wheat grains, the definitions of bran, endosperm and embryo are fuzzy but in broad terms the grains (on a dry matter basis) are composed of 15% bran, 83% endosperm and 2% embryo. The moisture content of grains will vary depending on environmental factors; figures of 12±20% in the field are not uncommon while in the mill 12±15% are more likely. In whole grain an approximate analysis (% dry matter) would be: Sugars Starch Pentosans (soluble proteins) Protein Lipids (fats) Cellulose Minerals

2.5 71.5 3.5 15.0 2.5 3.0 2.0

The distribution of the different components throughout the grain is not uniform with the cellulose and minerals more likely to be found associated with the bran and germ and most of the starch in the endosperm. Thus in the different milling processes employed to manufacture white flours there is a concentration of some of the grain components into the different milling fractions.

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In the manufacture of bread and fermented products it is the proteins which are of greatest concern since they have the ability to form a gluten network capable of trapping the carbon dioxide gas generated by bakers' yeast fermentation; both the quantity (BPS, pp. 18±19) and the quality (BPS, p. 20) impact on the dough gas retention and processing properties. The most functional proteins for breadmaking are those largely found in the endosperm of the grain. The pentosans, or soluble proteins, make a significant contribution to the water absorption capacity of the flour (BPS, p. 27) because of their ability to absorb about seven times their own weight of water (Stauffer, 2007) which is 3± 4 times more than any other flour component. However, because they are present at low levels in flour their overall contribution to water absorption capacity is small. Starch plays a number of roles in baked products. During the manufacture of many baked products starch in the presence of water and upon heating undergoes a transformation known as gelatinisation and in this form is a significant contributor to structure formation, especially in cakes. In bread the gelatinisation of starch and its subsequent retrogradation in the loaf during storage is a key element of the staling (firming) process. During the wheat milling process some of the starch is physically damaged, which contributes to its functionality in baking (BPS, 25±6). Cellulose is most often linked with the bran content of the flour, which tends to have a negative effect on flour properties, especially dough gas retention (see 2.2) but makes a positive contribution to dietary fibre. The naturally occurring sugars in wheat grains are not usually considered to be important but it is worth noting that in the manufacture of bread and fermented products they do contribute to supporting yeast fermentation. The minerals and vitamins present in wheat grains contribute to the nutritional value of flours. The lipids present in wheat flour are mostly associated with the germ (Cornell, 2003) and to a lesser extent the bran. Their role in baking has not yet been clearly defined, in part because in order to study them it is first necessary to extract them from wheat flour and this may lead to a modification of their functionality which is not representative of how they would work in the original flour. References

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. CORNELL, H. (2003) The chemistry and biochemistry of wheat. In (ed S.P. Cauvain) Bread making: Improving quality, Woodhead Publishing Ltd, Cambridge, UK, pp. 31±70. LORENZ, K.J. and KULP, K. (1991) Handbook of Cereal Science and Technology, Marcel Dekker Inc., New York, NY. STAUFFER, C.E. (2007) Principles of dough formation. In (eds. S.P. Cauvain and L.S. Young) Technology of Breadmaking, Springer Science + Business Media LLC, New York, NY, pp. 299±332. CAUVAIN, S.P.

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2.4 We understand that millers often use a mixture of different wheats to manufacture the flours that they supply to us. Can you explain why they do this? In every country where wheat is grown there are many varieties; in some cases the numbers may run close to or exceed 100. Modern wheat varieties are the result of selective breeding over many years as humankind matched wheat variety with climate and soils in the different parts of the world. The type of wheat grown is largely determined by environmental conditions such as the nature and length of the growing season. In the UK and elsewhere it possible to sow and grow wheat to over-winter and harvest in the autumn but in some parts of the world the severity of the winters may restrict wheat growing to spring planting alone. Often the focus of selective wheat breeding in the past was related to agronomic and economic factors such as increasing yield and building disease resistance. It is perhaps only in the last 40±50 years that greater attention has been paid to developing wheat varieties for their baking and end-use performance. Many bakery products and processes are closely linked with and traditionally based on the qualities of the locally grown and available wheat. In practice this means that taking wheat grown in one part of the world and using it to make a different product in another part of the world is not always successful without recipe or process adjustment. Try making a baguette with 100% strong Canadian wheat and the product is quite different from using French-grown wheats, and the reverse would be largely true in that French-grown wheats would not make good quality North American pan bread without adjusting the recipe and process used. The milling characteristics of individual wheats also vary. There are few examples of wheats which yield the `perfect' flour for a given bakery product and process. Even if there were, it is important to recognise that the quality characteristics of wheat drift with time. This is a well-known botanical problem seen with all plants. In practice new wheat varieties need to be developed on a regular basis to ensure an adequate supply of wheat of the appropriate quality for bakers. Even bakery processes change with time and this presents new challenges for millers to match their flours to those changes. The choice of wheats used by millers in their grist is influenced by factors such as the availability of different wheat types, both local and imported, and the manner in which their milling process is structured. Not all millers blend wheats before milling, some may mill wheat varieties separately and then blend the individual flours before sending the final product to the baker. There are advantages and disadvantages to the two ways of milling but discussion of these is outside the scope of this book. In summary, millers will have an intimate knowledge of the wheats available for their use and the likely performance characteristics of the flours that they will produce. By accessing and blending different wheat varieties they are seeking to deliver flours with the required performance characteristics and consistency for bakers.

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2.5 We have heard several experienced bakers talking about the `new harvest effect' and the problems that it can cause. Can you explain what is behind this phenomenon and how we can mitigate its effects? The `new harvest effect' is one of the great mysteries of the cereals world. It has been much discussed in the cereals industry but a lot of the evidence for its existence is apocryphal. There have been a number of scientific investigations related to the topic, generally with inconclusive results. It is said to be responsible for a number of different, usually unexpected, and occasionally catastrophic bread quality losses which occur around the period when wheat is newly harvested; these have included loss of bread volume and cell structure, but most commonly dough processing problems are the main issues that are identified by bakers. The basis for any effect is not clear but has variously been attributed to the ripeness of the wheat at harvesting, the short-term age of the wheat before it is incorporated into the milling grist and even the short-term age of the flour before it reaches the bakery. It is relatively uncommon for millers to make a complete transition from 100% òld' crop to 100% `new' crop; usually they will gradually increase the proportion of the new harvest wheat in the grist. In many parts of the world the global trading of wheat further complicates the transition as millers may be incorporating different new crop wheats at different moments in time. It is true that wheat quality does vary with different crop years but millers usually take this into account through suitable quality testing and adjust the mixed grist of wheats that they use accordingly (see 2.4). Milling and baking processes have changed considerably in the last 40 years and it may be that some of the past experiences that are re-told by bakers are no longer relevant. Those breadmaking processes which rely exclusively on the quality of the gluten network in the dough are likely to be the most sensitive to any changes in flour properties with harvesting year. In breadmaking processes where improvers and dough conditioners are added then the effects of small variations in flour quality are less likely to be noticeable. It is interesting to note that improver suppliers are known to make small changes to the formulation of the bread improvers around the new harvest period. The `new' harvest effect is not usually associated with minor changes, rather with more significant and unexpected quality losses. A common feature of these catastrophic failures is that they often disappear without apparent reason after a short period of time using the new flour has elapsed. One possible explanation is that in larger bakeries the process conditions have been settled and optimised for many months and are sensitive to the small changes in wheat quality, which inevitably occur from crop year to crop year. After a period of trial and error the problem usually dissipates as the plant is re-optimised to the new primary raw material quality. We are sorry that we cannot give you a more explicit explanation.

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2.6 We have the water absorption capacity of our flour assessed regularly but find that this is different to the actual water level that we use in the bakery. What are the reasons for this difference and is it important for breadmaking? The level of water that you add to flour for bread making depends on many factors, some determined by the properties of your flour, some by the requirements of the product you are making and some by the mixing and processing methods you use. The water absorption capacity of the flour tends to have less relevance in the manufacture of cakes, biscuits and pastries. There are a number of different methods by which the water absorption capacity of wheat flour is measured (for specific examples see Cauvain and Young, 2009). They are all commonly based on the principle of making a flourwater dough and measuring the rheological properties of that dough during mixing. As the dough mixes it exerts torque on one of the mixing arms and that torque is transmitted to a recording device, commonly a chart or digital display. The chart has a number of horizontal and parallel lines on it and is moving at a constant speed. As the flour begins to hydrate, the rheological properties of the flour-water mixture change and these are recorded on the chart. For flour water absorption estimation one of the horizontal lines is chosen as representing the desired consistency, and the amount of water added to allow the mixture to reach the chosen line is taken as the water absorption capacity of the flour. To some extent the chosen line is arbitrary and linked with a sensory (albeit expert) evaluation of the ìdeal' dough consistency. The choice of dough consistency for the standard method cannot take into account all of the potential recipe and process variations that are used in breadmaking and so the flour-water absorption capacity value you are given should only be seen as a guide as to what may be used in the bakery and more importantly perhaps, as a prediction of any changes that you may need to make in order to accommodate variations in flour properties. Contributions to the measured water absorption capacity of flour come from a number of individual flour properties. These include: · The moisture content of the flour; the higher the moisture, the lower the water absorption capacity. · The protein content of the flour; the higher the protein content, the higher the water absorption capacity. · The level of damaged starch in the flour; the higher the damaged starch level, the higher the water absorption capacity. Other contributions come from the enzymic activity and the level of pentosans (soluble proteins) but these are usually relatively small by comparison with the effects of the main flour components. Wholemeal, bran-supplemented and fibreenriched flours will always have a higher water absorption capacity than white flours because of the level of bran and fibre that will be present. The optimum consistency for a bread dough is hard to define because much depends on how the dough will be processed. Hand processing allows for sensitive handling of the dough with ready adjustment of the pressures, which will be applied

42


during moulding and shaping. When dough is mechanically processed, the processing equipment cannot adjust its pressures and so there is a much greater need for the consistency of the dough to be optimised and to remain as unvarying. In general, doughs which will be baked in a pan tend to have higher added water levels than those which will be baked on trays or the oven sole (i.e., freestanding). In the former case, a soft dough will more readily flow into the corners of the pans, while in the latter case, a stiffer dough will more readily retain its shape. For example, it is common to use lower water levels in the manufacture of UK-style bloomers, which traditionally have a round or oval cross-section. Too much water and the dough will flow during proof and yield an uncharacteristic and unacceptable flat shape. Some bread types depend on the production of a soft dough in order to achieve the required characteristics. In the manufacture of traditional French baguettes the added water levels may be several percentage points above the measured flour-water absorption capacity and above that used for pan bread production. The soft dough contributes to the ease of dough moulding and avoidance of the squeezing out of the large gas bubbles, which significantly contribute to the creation of the characteristic open cell structure of baguette. The individual dough pieces are proved in cradles of some form which stops them from flowing and the soft dough also contributes to the rapid expansion of the dough piece in the oven, which yields a high specific volume product. Cauvain and Young (2008) discuss the role of dough consistency and its impact on bread cell structure. They show how the gas bubble structure in stiff dough can be broken down and contribute to the formation of areas of damaged structure in the bread comprising coarse cell structure and dull coloured crumb (BPS, pp 87±8). While dough consistency may vary with product and process, there is one dough property that is commonly avoided in all cases, namely dough stickiness. In the bakery, problems with dough stickiness are usually associated with the water level added during dough mixing, and a common reaction to excessively sticky dough in the bakery is to reduce added water levels. A reduction in added water level may well improve the processability of the dough but high water levels per se are often not the main cause of dough stickiness. In many cases dough stickiness arises because of lack of dough development in the mixer; the greater the dough development, the higher the added water level may be. The other major contributor to apparent dough stickiness comes from subjecting the dough to shear forces during processing, such as during moulding, if these can be minimised then water levels can be optimised without compromising dough rheology and bread quality. References

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2008) Bakery Food Manufacture and Quality: Water Control & Effects 2nd edn, Wiley-Blackwell, Oxford, UK. CAUVAIN, S.P. and YOUNG, L.S. (2009) The ICC Handbook of Cereal, Flour and Testing: Methods and Applications, DEstech Publishing, Lancaster, PA. CAUVAIN, S.P.

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2.7 Why is the protein content of wholemeal bread flour typically higher than that of white flours but the bread volume is commonly smaller with the former? Protein is distributed throughout the different components of the wheat berry but that distribution is not uniform. There tends to be less protein in the central endosperm portions of the grain (Kent and Evers, 1994). This non-uniform distribution of wheat protein is mirrored by an increase in the starch content. The protein/starch `gradient' in the grain cross-section reflects the manner in which the endosperm develops in the growing plant as the different components are synthesised. The starch granules are packed into cells with the protein fragments. The cell walls of wheat endosperm are mainly composed of arabinoxylans. Surrounding the starchy endosperm is the aleurone layer with dense, thick cell walls. Further out in the grain cross-section are the different layers which characterise the bran. Since the distribution of protein is not uniform throughout the grain, the protein content of the flour is often a reflection of the milling processes used to manufacture the flour. By definition wholemeal flour represents all of the grain crushed into flour and so the protein content of the final flour should be the same of the original starting grain. White flours are based on the separation of the starchy endosperm from the surrounding bran layers and they tend to have around 1% less protein than the original grain (viz. wholemeal flour). The precise difference in the protein content of the grain and the white flour produced from it varies slightly according to the milling technique employed. The presence of bran reduces the gas retention properties of the dough, which commonly yields lower volume in the finished product unless modifications are made to the breadmaking recipe and process. While there are proteins in the bran particles they do not readily form a gluten network as is the case with the proteins in the endosperm cells; in practice this protein may be considered as `non-functional'. The mechanism by which bran particles reduce dough gas retention is not fully understood. Some views suggest that the particles of bran `puncture' the gas cell walls in the dough. However, it is more likely that the bran particles represent areas of discontinuity and weakness in the gluten network, which more readily allow the coalescence of smaller gas bubbles as they expand during proof and the early stages of baking and so permit the escape of some of the carbon dioxide gas being produced by the yeast. For the reasons given above it is common practice to produce wholemeal flours with much higher protein contents than that of white flours. This is done either by choosing a high protein wheat within the milling grist or through the supplementation of the milled flour with dried, vital wheat gluten (BPS, p. 23). References

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. KENT, N.L. and EVERS, A.D. (1994) Kent's Technology of Cereals, 4th edn, Elsevier Science Ltd., Oxford, UK CAUVAIN, S.P.

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2.8 We get a significant variation in the quality of our wholemeal bread and rolls depending on which flour we purchase. What characteristics should we look for in a wholemeal flour specification to get more consistent results? Wholemeal flours fall into two main categories: stoneground and roller-milled (BPS, p. 34). A key difference between the two is the particle size distribution; in general stoneground flours have a greater proportion of fine bran particles than the roller-milled type. It is well known that the presence of high levels of bran in wholemeal flours is responsible for the lower bread volume that is achieved by comparison with white flour from the same wheat, despite the fact that the white flour has a lower protein content. It is also known that finer bran particles tend to have a proportionally greater volume-depressing effect than coarse particles. In addition to the bran particle size difference there may be differences in the endosperm particle size of the two types of wholemeal flour. It is likely that the endosperm particle size of the stoneground form is coarser than that of the roller-milled type because the endosperm particles are subjected to considerably fewer grinding passages. One possible consequence of this difference is that the endosperm particles take longer to hydrate and if your mixing times are short, you may not see the same extent of gluten formation. You can check this with a few simple trials with extended mixing times. The protein content of your wholemeal flour should certainly be specified. This will reflect the protein content of the wheats chosen by the miller. It is possible to add vital wheat gluten to boost the protein content of your mix but gluten fortification is less effective with slower speed mixers (BPS, p. 23). The specification of the Hagberg Falling Number is as important with wholemeal flours as it is with white flours and you should also consider whether you should specify the water absorption capacity of the flours. You will need to remember that the water absorption capacity is only a guide as to what water level you will need to actually use for dough mixing. In the case of wholemeal flour this is an especially important point to bear in mind, since the bran and larger endosperm particles will be slow to hydrate. This often means that wholemeal flour doughs become stiffer during post-mixer processing and this can have a negative impact on dough handling properties and contribute to moulder damage and other product quality losses. You should try to maximise the water additions made to wholemeal flours, the initial tackiness that you observe when the dough has finished mixing should begin to disappear within a few minutes during processing. Optimising the added water level will also help you optimise dough development and the gas retention properties of the dough. Reference

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK.

CAUVAIN, S.P.

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2.9 Since enzymes such as alpha-amylase are inactivated by heat during baking, is it possible to use heat-treatment of flour to inactivate the enzymes in low Hagberg Falling Number flours before baking? The temperature at which alpha-amylase is inactivated depends on its source. There are three common sources: fungal, cereal and bacterial, which are inactivated at increasingly higher temperatures (BPS, pp. 59±60). Since you are asking about flour, then the source of the alpha-amylase is referred to as cereal (commonly from wheat, rye or barley). The exposure of flour to heat brings about a number of different changes. In addition to inactivation of the alpha-amylase there will be: · A loss of moisture. · The potential for denaturation of the protein. · Changes in the swelling and gelatinising characteristics of the starch. When heat is applied to flour it quickly loses moisture but as the moisture content falls to around 8% the rate of moisture loss with continued heating slows down. It appears to be that from this point on some of the more profound changes take place in flour properties. At low levels of heat input a reduction in the extensibility of the flour is usually observed (Kent-Jones, 1926). Prolonged heating leads to complete denaturation of wheat proteins and they lose their ability to form a cohesive gluten network in dough. Dry heat treatment of flour brings about changes in starch properties which are analogous to chlorination and this type of treatment is used to replace chlorination for flours intended for the manufacture of high ratio cakes and some other baked products (BPS, pp. 30±1). Heat treatment of flours should not be used where the product is intended for use in breadmaking. Thus, inactivation of alpha-amylase by heat should not be seen as a means of reducing the adverse effects of cereal amylase in breadmaking (BPS, pp. 57±8; Cauvain and Young, 2006). In some speciality flours, i.e. those destined for use in the manufacture of soups and sauces, inactivation of alpha-amylase is beneficial. In these cases the changes to the proteins and starch are acceptable, since they contribute to a discernible increase in batter viscosity. The changes which heat brings about increase the susceptibility of starch to amylase attack which would reduce the batter viscosity. With the amylase inactivated, batter viscosity can be maintained at an acceptable level. References

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2006) The Chorleywood Bread Process, Woodhead Publishing Ltd, Cambridge, UK. KENT-JONES, D.W. (1926) A study of the effects of heat upon wheat and flour, especially in relation to strength. Thesis presented to London University, UK. CAUVAIN, S.P.

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2.10 We are considering making traditional German-type rye breads and have researched the recipes and production methods. Do you have any suggestions as to what characteristics we should have in the rye flour? Rye grain is more susceptible to pre-harvest sprouting than wheat. The starch in rye flour gelatinises at a lower temperature than wheat starch and therefore rye flour is much more susceptible to enzymic degradation by alpha-amylase. Another fundamental difference is that the proteins present in rye do not form a gluten network to any significant degree and the pentosans in rye are essential for water binding in order to form a dough. Thus, while some of the grain and flour testing methods are common to wheat and rye flours, different emphases are placed on the results when incorporated into flour specifications. The key quality requirements for rye flours are: · Minimum Hagberg Falling Number of 90 sec. · Pentosan content of 7±10%. · Water absorption capacity 68±75%. The water absorption capacity of rye flour is typically higher than that of wheat flour because of the much higher level of pentosans in rye flour. It is common practice to measure the gelatinisation characteristics of rye flour. The technique comprises heating a rye flour-water mixture at a constant rate from 30 to 90ëC and following the changes in viscosity that occur over this temperature range while the mixture is stirred. A typical instrument used for this purpose would be the BrabenderÕ AmylographÕ which records changes in viscosity in Amylograph Units (AU). The AU value will be related to the enzymic activity in the flour, the lower the AU value the higher the enzymic activity and consequently the poorer the shape of the loaves and the lower their volume. At very low AU values splits and other defects may be seen in the bread crumb (see Fig. 9).

Fig. 9 Rye bread made with flours with different AmylographÕ viscosities (reproduced with permission of BrabenderÕ GmbH & Co. KG).

A range of rye flours are often available varying from 100% whole grain through to a refined flour with low bran content, which allow the production of a wide range of rye bread types. It is worth noting that the acidification of rye dough and on occasions the pre-treatment of the flour with heat (scalding) are two common ways of restricting the enzymic activity in the final dough.

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2.11 We have changed suppliers of our self-raising flour and find that we are not achieving the same product volume as before. If we adjust the recipe by adding more baking powder we find that the products tend towards collapse. Can you explain why and how do we overcome the problems? Self-raising flours contain the mixture of a food grade acid and sodium bicarbonate required for the generation of carbon dioxide gas (BPS, p. 36). It is possible for the loss of gassing power to occur with storage time but this is not usually a significant problem as long as the flour is kept dry. In many parts of the world there are standards governing the volume of carbon dioxide gas that should be released from self-raising flour but these are usually set as minimum rather than absolute levels (BPS, p. 36). It may be that your previous flour supply was providing more than the required minimum and this is why you are now suffering from a lack of volume. However, the fact that your products collapse when you add extra baking suggests that this is not the most likely cause of your problem. The different food grade acids which are permitted for use in self-raising flour have different rates of reaction with sodium bicarbonate (BPS, pp. 189±90). This is important in controlling the release of carbon dioxide during processing; too early and the products tend to lack volume, too late and the products may tend to collapse. The data in Fig. 10 compare the rates of reaction for two commonly used food grade acids. From the description of the problem that you have given it would appear that your new source of self-raising flour is giving an early release of carbon dioxide and the level of extra baking powder that you have added to compensate is simply too high; try gradually reducing the level that you add and you should find a point at which you retain the product volume while avoiding collapse.

Fig. 10 Rates of reaction of food grade acids.

Reference


CAUVAIN, S.P.

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2.12 We are a bakery working with a local farmer and miller to produce a range of local breads and want to use some different varieties and forms of malted grains that we are producing. Can you advise us on any special issues that we should be aware of? Adding grains in different forms to breads is a good way of introducing a variety of flavours and textures into your products. There are a few matters that you need to take into account in order to get the best results in your product. Wheat, barley and rye can be used to make malted grains and turned into a variety of granular products for adding to bread dough. One thing that you do need to be careful of is that the grain products are not hard and dry when you make them, as they can potentially cause unpleasant eating qualities if they are large particles. Two forms of grains are commonly used: crushed or flaked, and kibbled. The former will be prepared with a higher moisture content to aid preparation and so will be susceptible to mould growth. Steaming is commonly used to prepare grains for flaking. Kibbling yields much smaller pieces of broken grain which is very useful as a surface decoration. A key factor for you to consider is that the malting process initiates a significant level of enzyme activity in the grains and these enzymes will remain active in the dough. The amylase activity may cause problems with dough softening and contribute to side-wall collapse in the baked product (BPS, p. 83) or even keyholing in severe cases (BPS, pp. 57±8). If you do have this problem, then you may want to reduce the additions of other enzyme-active materials, such as malt flour, or use a less enzyme-rich improver if you are using a no-time dough process. There will be other enzymic activity to watch out for, most notably proteolytic activity, which contributes to dough softening and a weakening of the gas retention properties of the dough. The malting process generates complex sugars and these will also be carried into the dough with the malted grains. These should not be a problem but if you notice that the product crust colour becomes darker you may want to reformulate to reduce it. You may need to increase the protein content of the flour that you are using as the dough system will need to carry the non-functional malted grains. Reference


CAUVAIN, S.P.

Further reading

and THOMAS, D.A. (1991) Malted cereals: Production and use. In (eds K.J. Lorenz and K. Kulp) Handbook of Ceral Science and Technology, Marcel Dekker, Inc, New York, NY, pp. 815±832.

PYLER, R.E.

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2.13 Can we mix oats or oat products with our wheat flours to make bakery products? If so, are there any special issues that we should be aware of? Oats, in common with many other grains, are composed of outer bran layers, an embryo (germ) and starchy endosperm; the latter, in contrast with many other grains contains significant amounts of protein and is rich in oil. The first stage in oat milling is to remove the husk or outer hull to yield clean `groats'. Oat milling follows a similar pattern to wheat milling but is less complex. The groats may be cut, flaked or milled or ground to yield oat flour, sometimes with the bran being taken off separately. The high level of oil in oats (typically 5±9%) is distributed relatively uniformly through the oat components which are also rich in lipase. Unless the lipase is inactivated by heat, oat products are very quickly prone to rancidity. The process of inactivating the lipase enzyme is known as `stabilisation' and comprises heating the oats with steam for up to 2h at over 100ëC. The stabilisation process also contributes to the development of a `nutty' aroma and flavour in oat products. Cut oats are usually milled to oatmeal of different size grades and it is these products which are most commonly used in baking. Perhaps the best known bakery products which use oatmeal are biscuits and cookies, where they may be included on their own or along with fruits and nuts. Oatmeal biscuits have a strong regional bias associated with Scotland and they are a dense and friable biscuit with a distinctive flavour. There are other regional products which use oatmeal such as Staffordshire Oatcakes (see 8.4). The consumption of oat bran has been linked with the potential for lowering blood cholesterol in the human digestive system and this has led to its inclusion in a number of food and drink products. The àctive' ingredient in this context is the soluble fibre gum, beta-glucan. Oat flakes may find use along with other flaked grains in the manufacture of bread and rolls, either as part of the dough or as a surface dressing to provide texture. Oat bran and oatmeal are included in some breads where the distinctive aroma and flavour are seen as beneficial. The oat products are usually added to a strong white flour base since oats do not have the potential to contribute to the formation of a gluten network in the dough. There is a tendency for the bread products to have a slightly dry mouthfeel but when combined with a suitable filling, e.g. prawn mayonnaise, they make a popular sandwich type in the UK. Oat bran is also a key component of some speciality cake muffins. Further reading

and MCCONNELL, J.M. (2001) Oats. In (eds D.A.V. Dendy and B.J. Dobraszczyk) Cereals and Cereal Products, Aspen Publisher, Inc., Gaithersburg, MA, pp. 367±391.

WELCH, R.W.

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2.14 We wish to add non-wheat fibres to some of our baked products to increase their healthiness. What fibres can we use, in what products and what potential technical problems should we be aware of? What is resistant starch and can it be used in bakery products? There are a large number of fibres from many different sources that might be and have been proposed as additions to baked products. The range is so wide that it is not possible in a short answer to do more than offer some general pointers and a few examples. If you are going to make health claims then it is important that you first make sure that the fibres that you are proposing to use are permitted as additions to bakery foods and to identify any restrictions that might apply. You should also carefully check the potential validity and permissibility of any health-related claims that might be used on the product packaging or in any advertising and marketing promotions that you might wish to undertake. Health-related claims are becoming increasingly restricted in order to avoid misleading consumers. One of the more difficult issues will involve the definition and measurement of dietary fibre. As yet there is no universally accepted definition, though a statement by the European Food Safety Authority (EFSA) to the European Commission in 2007 concluded that a definition of dietary fibre `should include all carbohydrate components in foods that are non-digestible in the human small intestine' and went on to list such components as including `non-starch polysaccharides, resistant starch, resistant oligosaccharides with three or more monomeric units, and other non-digestible, but quantatively minor components when naturally associated with dietary fibre polysaccharides, especially lignin'. In the same statement EFSA commented on analytical methods available for the measurement of dietary fibre and considered that for practical purposes a single assay would be advisable but did not recommend what that might be. The definition of dietary fibre is also being considered at the time of going to press by the Codex Alimentarius Commission of the Food and Agricultural Organization of the United Nations. A common technical issue when you add fibres to bakery product recipes is their ability to absorb water, which necessitates an increase in recipe moisture levels. This is not usually a problem with bread dough or cake batters but can be a problem in the manufacture of biscuits and pastries where the requirement is to ensure that the extra water is baked out so the final products retain their crisp and hard eating characteristics. It is almost certain that any fibres that you add will contribute little or nothing to the formation or stabilisation of bakery products structure. This poses a number of issues, mainly for bread and cake making. In the case of bread, you may need to add extra protein or adjust the dough conditioner/improver to ensure that there is no loss of volume. In cake recipe balance, the extra water that is added along with fibres to maintain a suitable batter viscosity may require adjustment of the sugar levels in the recipe. You will need to be careful that the

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sugar and liquid levels do not exceed acceptable levels for the flour that you are using (e.g., treated or untreated). In practice the level of fibre addition is relatively low and can usually be included as `flour' when balancing recipes. Fibres come in many different forms from fine powder through flakes to whole grains and seeds. Choosing the form you want to use will depend on the product effect that you want to create; for example, whether you want the fibre to be visible, whether you want it as a surface finish or whether you want it incorporated directly into the dough or batter. Some of the fibrous grains and seeds have other interesting attributes related to their nutritional properties. In many cases the attraction of using a particular fibre is that they have a colour which is lighter than that of wheat bran and similar to that of wheat flour. The addition of such materials allows you to increase the fibre content of the product without detracting from the appearance of its crumb. This is often seen as an advantage in delivering the nutritional benefits of fibre to children. Some types of starch are more resistant to digestion in the large intestine than others and are considered in medical terms to act like dietary fibre and are known by the generic descriptor `resistant starch'. The term actually covers four types of resistant starch (RS): · RS1 ± considered to be physically inaccessible as part of intact or partly milled grains. · RS2 ± resistant starch granules in their `natural' form as might be found in potato, green bananas, some legumes and high amylose starches. · RS3 ± retrograded starches from typical sources such as cooked and cooled potato, bread crusts and some flaked products. · RS4 ± includes a wide range of modified starches. Further reading

(2003) High-fibre baking. In (ed. S.P. Cauvain) Bread making: Improving Quality, Woodhead Publishing Ltd, Cambridge, UK, pp. 487±499. LORENZ, K.J. and KULP, K. (1991) Handbook of Cereal Science and Technology, Marcel Dekker, New York, NY. MCCLEARY, B.V. and PROSKY (2001) Advanced Dietary Fibre Technology, Blackwell Science, Oxford, UK. KATINA, K.

3 Other bakery ingredients

3.1 We wish to reduce the level of salt (sodium chloride) that we use in our baked products. What do we need to be aware of when making reductions? Salt (sodium chloride) has a number of different functions in the manufacture of bakery products, some of which are product specific. The most immediately recognised one is to contribute to the flavour profile of the product. Salt has its own characteristics and is considered as one of the five basic tastes (the others are sweet, acid, bitter and the recently added, umami). In addition to its own distinctive flavour salt plays a significant role in enhancing other, often more subtle, flavours. Reductions in added salt levels in baked products are usually detected very readily by consumers, so we recommend that you make small but progressive reductions over a period of time so that the palate of your customers becomes èducated' for lower salt levels. Sodium chloride is one of very few chemicals which confer a salty flavour and it is not easy to `replace' the flavour contribution with other ingredients. Potassium chloride may be used to replace the sodium salt but, as the level of potassium chloride increases, there is a development of an unacceptable level of bitterness in the product. Each of the salt `replacers' that are offered has a distinctive flavour profile but all are different from sodium chloride. Other flavours enhancers are offered for use in lower salt foods but their suitability for use depends on the food in which they are to be used. In breadmaking, a possible route to increasing the flavour of bread is by using fermentation of all or part of the dough in the manufacturing process. However, it should be noted that the overall flavour profile of the final product will be different and may be less acceptable to all consumers. Again it may be a matter of educating the consumer palate. The other universal function of salt in baked products is that of a preservative. Additions of salt have been used to extend the mould-free shelf-life of cakes and

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many other bakery products (Cauvain and Young, 2008). Weight for weight salt is 11 times more effective than sucrose at reducing the water activity of baked products and so it has been a common addition to many recipes. If you are going to use lower salt levels then you may have to compensate for the increase in water activity with other anti-microbial strategies. In high water activity products (e.g., bread, hot-plate goods) the impact of salt on product mould-free shelf-life is very small. However, the water activity levels in such products are marginal for rope spoilage (BPS, p. 86) and so reductions in added salt levels should be approached with some caution. Rope spoilage is more likely to be a problem in wholemeal and mixed grain breads as the spore-forming bacteria are associated with the other layers of grains and so spore counts are likely to be higher. Salt plays some technological roles in the manufacture of bread and other fermented products. One of these is to limit the activity of bakers' yeast in the dough. Reductions in added salt levels will lead to increased gas production by the added yeast such that the dough may become òver-proved' in a standard proof time in the bakery. In such cases it may be necessary to either reduce proof times or lower added yeast levels in the dough; the latter is most commonly preferred, as the length of time used for dough proving has other technological benefits related to the rheological properties of the gluten in the dough; most notably to contribute to the uniformity of oven spring when the product is baked. Salt also makes a contribution to dough development and bread volume. Danno and Hoseney (1982) showed that Mixograph times to peak were shorter when salt levels were reduced, while other studies (Miller and Hoseney, 2008) have shown that loaf volumes were optimised at around 2% flour weight and that volume decreased when salt levels were both increased and decreased. Any losses in bread volume can be compensated for by other ingredient and recipe adjustments. Lowering salt levels in bread dough does lead to some adverse changes in dough rheological properties after mixing. In particular there is an increase in dough stickiness which may be of concern in highly automated plants or where ambient dough-processing temperatures are high. References

and YOUNG, L.S. (2001) Baking Problems Solved. Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2008) Bakery Food Manufacture and Quality: Water Control and Effects, Wiley-Blackwell, Oxford, UK. DANNO, G. and HOSENEY, R.C. (1982) Effect of sodium chloride and sodium dodecyl sulphate on mixograph properties. Cereal Chemistry, 59, 202±204. MILLER, R.A. and HOSENEY, R.C. (2008) Role of salt in baking. Cereal Foods World, Jan± Feb, 4±6. CAUVAIN, S.P.

Further reading

and ANGUS, F. (2007) Reducing salt in foods: Practical Strategies, Woodhead Publishing Ltd, Cambridge, UK.

KILCAST, D.

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3.2 What alternatives are there to using sodium chloride (common salt) in the manufacture of bread products? And how can we reduce sodium levels in our other baked products? Sodium chloride plays a number of significant roles in the manufacture of baked products besides that of conferring flavour. In doughmaking, the water activity effect has a direct impact on the development of the gluten structure in the dough and the rheological properties of the dough during processing. Some of the most important roles are associated with the control of water activity in dough and the baked bread and cakes. The strong effect of salt arises because of its ionic nature and its ability to form strong bonds with water molecules, thereby making them less available for a number of key baking reactions. In considering alternatives to sodium chloride for baked goods, the first point to note is that sodium chloride has a unique flavour. Its flavour profile is not shared with the other chlorides. For example, the direct substitution of sodium with other chlorides leads to baked products with an unacceptable bitter taste which is hard to mask; partial replacement at low levels is possible. At present the best option in bread is to seek to gradually reduce the level at which sodium chloride is added to bakery product formulations (see 3.1). While a number of `salt-replacers' are offered, most of these are in the context of boosting flavour when sodium chloride levels in recipes are being reduced. Most (if not all) of these replacers do not have the same functionality of sodium chloride with respect to dough structure formation and the control of water activity in the baked product and the restriction of microbial activity. Sodium-based compounds are common ingredients of the baking powders used in chemically raised baked products. Potassium and calcium bicarbonates may offer alternatives to the sodium form and non-sodium baking acids are already available. A key requirement when making a switch to a reduced or nonsodium baking powder will be to ensure that the rates of reaction in the baking powder are matched to the product requirements in order to avoid product quality losses. Even if baking powder reaction rates are matched with non-sodium baking powders, the residual salts from the reaction will have a different flavour profile from the sodium-based types and you will need to ensure that this is acceptable to consumers. Further reading

and ANGUS, F. (2007) Reducing Salt in Foods; Practical Strategies, Woodhead Publishing Ltd, Cambridge, UK.

KILCAST, D.


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3.3 We have seen references to a `lag phase' for bakers' yeast; what does this mean and what are the implications for baking? Bakers' yeast (Saccromyces cerivisii) is one of many different types of yeast which may be used or found in foods (Boekhout and Robert, 2003). Like all microorganisms, when placed in a suitable environment they begin to feed, and multiply. This process starts very slowly but as time progresses the rate of activity increases if the temperature remains constant and there is a ready supply of food. The key function of bakers' yeast in baking is the production of carbon dioxide gas. Modern strains of bakers' yeast are far more reliable than those that have been used traditionally. In the flour there is an initial supply of naturally occurring sugars (typically 1±1.5% by weight, see 2.3) and these are fermentable by the yeast. Later, as the combination of alpha- and beta-amylases in the dough get to work on the damaged starch granules, more sugar in the form of maltose becomes available to support fermentation. Sugars may be added to the dough formulation though in no-time dough processes the addition of extra sugar to support fermentation is not usually necessary but it may be added for its contribution to flavour and colour. Once the yeast has been added to the dough it takes a short while before its activity is sufficient for the generation of carbon dioxide gas and during this `lag' phase there is little change in the dough density. If we were to measure the density change with time after mixing, we would see little change for some minutes. Later dough density begins to fall as the carbon dioxide gas begins to diffuse into the gas bubbles in the dough and they expand. Typically the lag phase lasts around 10 minutes. This has limited impact when bulk fermentation processes lasting some hours are used for breadmaking but in no-time dough production the impact can be significant. The main effect of the yeast activity post-lag phase with no-time dough production will be seen in the divider and in particular on divider weight control. If a large bulk of dough is being divided volumetrically it is not unusual to see a drift in weight with dough standing time in the hopper. One of the advantages gained from the yeast lag-phase is that it will limit dough density changes and thereby improve divider weight control. Thus, in larger automated bakeries it can be of particular advantage to keep dough batch size at a level which requires the production and processing of an individual batch of dough in less than 10 minutes or so (Cauvain and Young, 2008). References

and ROBERT, V. (2003) Yeasts in Foods, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2008) Bakery Food Manufacture and Quality: Water Control & Effects 2nd edn, Wiley-Blackwell, Oxford, UK. BOEKHOUT, T.

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3.4 Are there any particular precautions that we should take in handling, storing and using bakers' yeast in the compressed form? In order to optimise the performance of bakers' yeast (Saccromyces cerivisii) in the manufacture of bread and fermented products it is important to ensure that it is kept in its optimum condition. Individual yeast cells are characterised by having a membrane which encloses the cell contents (Williams and Pullen, 2007). It is the latter that provide the yeast with its ability to produce carbon dioxide, ethanol and reproductive powers. In addition to providing a container for the cell contents, the membrane plays a critical role in regulating the flow of nutrients into and by-products (e.g., carbon dioxide) out of the cells. The flow of nutrients is controlled by osmotic pressure (Cauvain and Young, 2008). Compressed yeast is prepared under carefully controlled conditions in the factory (Williams and Pullen, 2007). A key requirement is that the cells (approximately 15 thousand million per gram) are intact (undamaged) and viable (alive). To ensure this and to minimise activity in the block, compressed yeast is commonly delivered at refrigerated temperatures, typically 4±8ëC and should be held at these temperatures until required for use (BPS, pp. 66±7). The particular precautions that you should take include: · Transfer the yeast as quickly as possible into refrigerated storage as soon as possible after delivery. Prolonged exposure to warm temperatures can lead to loss of activity through autolysis. This process is characterised by a darkening of the corners of the blocks, which may also spread along the edges of the blocks (BPS, p. 68). · Avoid having large quantities of yeast standing in the warm bakery waiting to be used. Try to establish a working pattern that draws out sufficient yeast for 1±2 h of production throughout the day. · Break down large blocks into a coarse crumble before adding it to the mixer as this will aid its dispersion throughout the dough. You may want to disperse the crumbled yeast into some of the recipe water before you use it but this is not essential with modern yeast strains and breadmaking practices. · Do not keep using the yeast after its shelf-life date has expired. There is a slow but progressive loss of gas production power in the yeast during storage, even under ideal refrigeration conditions (see Fig. 11). This will result in an increase in proof time or require the addition of extra yeast to maintain product proof volume. It may also lead to loss of bread volume through the action of glutathione from any yeast cells which have died. · Do not leave compressed yeast blocks unwrapped for long periods of time as they can dry out and lose activity. · Ensure that the conditions under which the yeast is stored remain optimum. It is important that the cell membranes remain intact. Amongst the cell contents are powerful reducing agents known as glutathione. This material is able to reduce the gas retention properties of gluten and also causes excessive flow of dough in the prover.


57

· Fluctuations in storage temperatures can lead to the formation of unwanted mould colonies on the surfaces of the blocks if they have been exposed unwrapped to the atmosphere and so should be avoided. · Avoid freezing the blocks as the formation of ice crystals inside the cells, their growth during storage and subsequent defrosting results in rupturing of the cell membranes and the release of the cell contents.

Fig. 11 Effect of yeast storage time on gas production.

References

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2008) Bakery Food Manufacture & Quality: Water Control and Effects 2nd edn, Wiley-Blackwell, Oxford, UK. WILLIAMS, T. and PULLEN, G. (2007) Functional Ingredients. In, Technology of Breadmaking 2nd edn (eds S.P. Cauvain and L.S. Young), Springer, New York, USA, pp. 51±91. CAUVAIN, S.P.

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3.5 What different types of bakers' yeast are available? Would there be any particular advantages for us to use an alternative to Saccromyces cerivisii in the manufacture of our fermented products? Yeast suppliers have many forms of Saccromyces cerivisii for use in the manufacture of bakery products. The compressed or block form used in many countries is both economical and practical. The yeast blocks are paper wrapped to limit exposure to air and to maintain humidity and limit moisture migration, which ensures better keeping qualities and active shelf-life. It comes in varying sizes from small cubes of approx 40 g to blocks of 0.5 to 2.5 kg. It can also be purchased as crumbled yeast. It should be stored in a refrigerator running at between 2 and 10ëC, ideally around 4ëC (BPS, pp. 66±7). The shelf-life of compressed yeast kept under the conditions recommended by the suppliers is between 4 and 8 weeks. Williams and Pullen (2007) showed how storing high activity compressed yeast at 15ëC for 14 days has a reduced activity to such an extent that that proving time of the dough in which it was used roughly doubled. Poorly kept compressed yeast quickly displays visible signs of deterioration, such as dark brown patches (BPS, p. 68). Dried and granulated (Fischer and Volker, 2008) yeasts are popular where a longer shelf-life product is required or where refrigeration is not practical, e.g. in warm climates. It comes in standard or instant forms. The instant form of dried yeast is available in vacuum packs and can be incorporated directly into the dough while the standard dried yeast needs to be hydrated before it is used. In their various forms dried yeasts have shelf-lives of up to two years. Some forms of dried yeast may also be incorporated into premixes for bakery products. Liquid or cream yeast is increasingly popular in modern plant bakeries as it is easily accurately and automatically dispensed into the mixing bowl. It is held in storage tanks which are gently agitated to prevent separation. In baking terms 1.5 kg liquid yeast is equivalent to 1 kg of compressed yeast for gas production. The shelf-life of the product is much shorter than the other bakers' yeast forms at between 10 and 14 days. Care needs to be taken to keep its storage temperature between 2 and 4ëC and the storage tanks should be cleaned out on a regular basis to reduce the risks of contamination with unwanted yeasts, moulds or bacteria which may result in the development of sour aromas and flavours in the dough. Frozen forms of bakers' yeast are also available from some suppliers. These products should be stored at ÿ18ëC and have shelf-lives of up to two years. They are usually added to the dough in the frozen form. The dry matter varies in the different forms of yeast from approximately 20% for liquid yeast to 95% for the dried yeast. If you are going to change from one form to another then the water level added to the dough will need to be adjusted according to the dry matter content of the different forms. There are different strains of Saccromyces cerivisii available and the yeast supplier will cultivate these to offer specific yeast for different baking products


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and processing methods. For example, the strain used for dough making in the Chorleywood Bread Process is able to generate carbon dioxide at a faster rate then other strains and avoids a `dip' in gas production at the critical moment when the dough pieces reach the oven (Williams and Pullen, 2007). While such yeast strains have a high fermenting power, they tend to be less stable and have a shorter shelf-life than other strains. For the production of sweet dough that is high in sugar (usually sucrose or dextrose) there are osmo-tolerant yeasts. These are able to cope with the increased osmotic pressure in the dough rather than being inhibited by the presence of the sugars (Williams and Pullen, 2007). There are strains which are better adapted for use in acid, low pH dough and others which are able to better perform when calcium propionate is present in the recipe. In principle any microorganism which is able to ferment sugars to produce carbon dioxide gas could be used in breadmaking. There are a large number of yeasts which would fit into that category which may come from the distilling and wine-making industries. Indeed yeasts from the brewing and distilling industries were the traditional source of gas production for bakers. Improved growth, osmo-tolerance, freeze-tolerance or aroma applications, have suggested the use of strains from Candida or Torulaspora. A few non-typical bakers' yeast strains have been patented for cold dough and nutrition applications and especially for stress tolerance; these include Saccromyces rosei, Saccromyces rouxii and Torulaspora delbrueckii. The availability of strains of Saccromyces cerivisii specifically for use in the manufacture of fermented products in bakeries is now highly developed and discussions with your supplier should help identify the type of yeast that is the most appropriate for the manufacture of your own products. References

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. FISCHER, G. and VOLKER, L. (2008) Granulated yeast. f2m baking+ biscuit international, 6, 40±43. WILLIAMS, A. and PULLEN, G. (2007) Functional ingredients. In (eds. S.P. Cauvain and L.S. Young) Technology of Breadmaking 2nd edn, Springer Science+Business Media, LLC, New York, NY, pp. 51±92. CAUVAIN, S.P.

Further reading

and ROBERT, Cambridge, UK.

BOEKHOUT, T.

V.

(2003) Yeast in Food, Woodhead Publishing Ltd,

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3.6 What effect does vinegar have on bread and why is it added? Vinegar has the advantage of being considered by many as a natural preservative. The chemical name for vinegar is acetic acid (E260) and it is sometimes known as ethanoic acid. It has been used for many years as an inhibitor for the growth of rope bacteria (Bacillus subtilis) in bread. As a preservative it has little intrinsic anti-microbial activity and so is added to increase the acidity (reduce the pH) and retard the initial growth of the bacteria. Rope spores are present naturally in the soil and can be found on the outer parts of the wheat grain. They are also present in the air and can be passed on in flour or by equipment which has been in contact with contaminated dough (BPS, p. 86). The white spirit form of vinegar is diluted to a give a 12.5% solution and added at the rate of about 1L per 100 kg flour; equivalent to a rate of acetic acid addition of 0.125% based on flour weight. Such levels reduce the bread crumb to a pH of about 5.4; the general level suitable for protection from rope. The level of addition required for wholemeal breads is slightly higher. To achieve a pH of 5.4 the amount of vinegar added will vary from one type of bread to another depending on the pH of the ingredients, the natural buffering effect of the flour and whether the flour has been fortified with calcium carbonate. All flours have a buffering effect on the efficacy of the acetic acid with the buffering being greater in flours with higher levels of bran. Figure 12 shows the effect of acetic acid addition on the pH of breads. Vinegar has a small effect on the gassing rate of yeast and so yeast levels may be slightly increased to counter this and reduce the impact on proof time.

Fig. 12

References

The effect of acetic acid addition on the pH of breads.

and YOUNG, LS. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK.

CAUVAIN, S.P.


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3.7 What ingredients are commonly used as preservatives? Are there any particular benefits associated with different ones? The choice of preservative depends on the product type and the potential microogranisms which are prevalent in causing spoilage. Microbial spores are airborne in the bakery environment and also present in the dry ingredients (flour), their packaging and through contact with contaminated equipment and surfaces. Preservatives only inhibit spoilage ± they do not destroy the microorganisms and so good hygiene is a necessary adjunct to using preservatives. A comprehensive list of preservatives for use in bread and fine bakers' wares is given by Williams and Pullen (2007). Breads and other fermented products are high in moisture and are susceptible to microbial attack. Table 7 shows some of the commonly used preservatives along with their recommended levels of use within the European Union; there are other local limits for their addition and these should be checked before use. Using the materials at their recommended levels should ensure an extension of mould-free shelf-life by 2±3 days at temperatures of 20ëC. Vinegar is used to combat `rope' bacterial spoilage and has a small inhibiting effect against moulds (see 3.6). Table 7 Common preservatives for bread and fermented products Preservative against moulds Calcium propionate Propionic acid Sodium propionate Sodium dipropionate

Recommended usage (% of flour wt) 0.2 0.1 0.2 0.2

For flour confectionery products, such as cakes and muffins with intermediate moisture levels, the commonly used preservatives are sorbic acid and its salts. They are not efficacious in bread and fermented products as the levels required render the dough sticky and difficult to process, inhibit the action of bakers' yeast and yield products with poor volume and coarse, open structure (unless added in their encapsulated form). Sorbic acid and its easier handled salt ± potassium sorbate ± can be added up to 2000 ppm (in the finished product). The levels used depend on the product water activity and pH. Adding preservatives to give more than a 50% extension to shelf-life is not usually recommended (Cauvain and Young, 2008) as the preservative flavour can often be detected by the consumer. The lower the pH of the product, the greater the preservative effect as shown in Fig. 13. Acetic acid and its salts may be used in many bakery products (see 3.6), although they are less effective than others mentioned here. In some cases the use of acetates rather than propionates and sorbates may reflect local legislation or commercial preferences. As with all preservatives high levels of addition

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Fig. 13 Additional days' shelf-life obtained in cakes of different pHs when treated with sorbic acid at 1000 ppm product weight.

produce distinctive odours and taste in the products and once consumers have become accustomed to these it may be difficult to interchange them. For products such as Danish pastries with relatively short shelf-life, preservatives are less commonly used. If the pastries are fermented then the preservatives used in breads would be suitable and for cake-like ones sorbic acid and its salts would be appropriate. For low moisture biscuits and cookies mould growth is not usually a problem and so the addition of preservatives is not common. In some cases it may be appropriate to use a combination of preservatives to achieve the desired effect on shelf-life. This is because there are many different types of moulds and each of them can tolerate a slightly different set of conditions and type of preservative. In most manufacturing environments it is unlikely that the full range of mould types contaminating a product will be known. There are some very common ones (e.g., penicillium sp., aspergillus sp.) and usually the addition of one preservative is all that is required. However, in some cases a `broad spectrum' approach with a mixture of preservatives (and other inhibitory processes) may be used to ensure maximum impact. With mixtures of preservatives the extension of the mould-free shelf-life of the product may be increased beyond that achieved with a single preservative, though the overall impact may be difficult to quantify. References

and YOUNG, L.S. (2008) Bakery Food Manufacture & Quality: Water Control and Effects 2nd edn, Wiley-Blackwell, Oxford, UK. WILLIAMS, T. and PULLEN, G. (2007) Functional Ingredients. In Technology of Breadmaking 2nd edn (eds S.P. Cauvain and L.S. Young), Springer, New York, USA, pp. 51±91. CAUVAIN, S.P.


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3.8 We have heard that alcohol can be used as a preservative. How is this achieved? The use of alcohol as a preserving agent has been known for many years. Christmas cakes are often treated with alcohol after baking to add flavour and benefit from the preservative and anti-staling properties. Ethyl alcohol can be an effective preservative for breads. Added at levels between 0.5 and 3.5% of loaf weight it gives good extension of shelf-life (Legan, 1993). Figure 14 shows the percentage increase in mould-free shelf-life obtained when ethyl alcohol is added (Seiler, 1984). The effect is obtained whether the alcohol is added to or sprayed onto all surfaces of the loaf before packing and sealing. If the alcohol is coated on the inside of the bag before inserting the loaf and sealing, the increase in shelf-life is similar. The alcohol acts as a vapour pressure inhibitor and discourages moulds from growing. In the case of bread, addition of alcohol at levels higher than 1% of product weight can usually be detected by the consumer. If adding alcohol to fermented products or cakes, checks should be made on possible local excise duties payable and on any labelling issues. Although it may be costly to use alcohol as a preservative, it has significant potential for its antimicrobial properties and for anti-staling in bread and cakes (Pateras, 2007).

Fig. 14

Relationship between alcohol concentration applied and percentage increase in mould-free shelf-life.

References

(1993) Mould spoilage of bread: The problem and some solutions. International Biodeterioration and Biodegradation, 32, 33±53. PATERAS, I.M.C. (2007) Bread spoilage and staling. In, Technology of Breadmaking 2nd edn (eds S.P. Cauvain and L.S. Young), Springer Science+Business Media, New York, pp. 275±298. SEILER, D.A.L. (1984) Controlled atmosphere packaging for preserving bakery products. FMBRA Bulletin No. 2, April, Campden-BRI, Chipping Campden, UK, pp. 48±60. LEGAN, J.D.

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3.9 What are the possible alternatives to chemically based preservatives? With the desire for `clean' labels bakers have sought the help of ingredients with natural preservative properties. Bakers have known for centuries the preservative effect of using dried fruit, e.g. raisins, in their cakes and other products. Sorbic acid salts develop on the skins of the fruit as they dry and, together with the higher concentration of sugar within the fruit, contribute to the longer shelf-life of the product. Such preservatives will inhibit microbial growth but will not prevent bacterial activity. It should be noted, however, that for a truly `natural' dried fruit, the fruit should not have been treated with sulphur dioxide during the drying process. Many red-berried fruits have sorbic acid present as part of their composition and if added as a fruit concentrate, might add a small preservative effect. In many cases the preservatives found in fruits act best at low pHs, e.g. circa 2.0, and so are effective when used in acidic products such as fruit juices but will have a limited effect in the higher pH bakery products (as a general rule bakery products lie in the pH range 5.0 to 6.5). Benzoates, which are found naturally in cranberries, also work best at low pH. Using acid dough components, such as fermented wheat flour, in bread can provide a preservative effect. This is based on the natural lowering of the pH of the dough from the actions of lactic and acetic acid bacteria. To speed up acidification a special culture of lactobacilli is added. For white breads, sufficient acid dough should be added to bring the pH to below 5.0. In order to prevent rope an addition of 10% of acid dough in the final dough mix should be sufficient and it is claimed has the benefit of improving the flavour of the bread. Salt (sodium chloride) is a natural preservative. It occurs in sea water and also is mined. It works by locking up the water in the bakery product so that the moulds cannot use the moisture for growth. However, its addition is limited by taste and more recently by concerns over the level of sodium chloride in the diet. Similarly sugar can be used to extend shelf-life and again its addition has to be carefully considered as it may have an effect on the processing and the final product quality (Cauvain and Young, 2008). Many of the chemically based preservatives are `nature identical' and have been given E numbers to denote their acceptance for use in food products. Often they have been derived from organisms that occur in nature. Their dosage and effectiveness are well known. The variability in the potential effectiveness of `natural' (non-chemically based) preservatives needs to be considered when relying solely on them in products. Reference

and YOUNG, L.S. (2008) Bakery Food Manufacture & Quality: Water Control and Effects 2nd edn, Wiley-Blackwell, Oxford, UK.

CAUVAIN, S.P.


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3.10 What type of sugar (sucrose) should we use for the different products that we make in our bakery? Sugar (sucrose) has a number of different functions in baked products; in addition to the obvious contribution to product sweetness, it also has an impact on the formation of product structures, which in turn influences texture, eating qualities and shelf-life, both sensory and microbially (Cauvain and Young, 2006). Sucrose is available in a number of crystalline and liquid forms (various types of syrups). In summary, the main forms of sucrose that are used in the manufacture of baked goods are: · Granulated ± usually the coarsest crystalline, refined white form. · Caster ± smaller crystals separated from the preparation of the granulated form. · Pulverised ± may be manufactured by re-grinding a crystalline form. · Icing sugar ± a fine, powdered sugar obtained by grinding crystals. · Demerara ± a light brown, crystalline sugar with pigments derived from the natural sugar cane. · Soft brown ± a mixture of small crystalline sugar and molasses. · Molasses ± a dark coloured syrup, the residue of the sugar cane refining process. Many of the functions of sugar in baked products require that it should be in solution in the mix. This does not necessarily mean that you have to prepare a sugar solution in the bakery. Sugar has a high solubility (typically sucrose dissolves in half its weight of water at 20ëC) but the quantity that can actually get into solution depends on the level of available water and the temperature of the mix. The size of the crystals is important in determining the rate at which they dissolve and in low water systems (e.g., biscuit dough) this can be a critical factor in deciding which form to use. Some of the key requirements for sugar properties are summarised for the different baked product groups below. Bread If used at all, relatively low levels of sugar are added in the manufacture of bread. The water levels are relatively high and dough processing times from mix to oven are relatively long by comparison with other baked products and usually sufficient time is available for any added sugar to readily dissolve. This means that most of the crystalline forms can be used without creating any specific problems. Fermented products (e.g., rolls and buns) Sugar is commonly added to rolls, buns and other similar fermented products to improve product sweetness and crust colour. The levels of addition still tend to be low enough to allow for the use of all the crystalline forms. You should note that high level of added sugar can have an inhibitory effect on yeast activity (Williams and Pullen, 2007).

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Sponges and cakes Caster sugar is the form most commonly used in the manufacture of sponges and cakes. While granulated sugar will readily dissolve in the water present in sponge and cake batters, there can be problems with re-cystallisation on the surface of the baked product (Cauvain and Young, 2008). A common phenomenon when sugar re-cystallisation occurs is the formation of small white spots on the crust (BPS, p. 167) and in less extreme cases the brown crust colour may be tinged with a grey haze arising from many small sugar crystals too small to be seen with the naked eye. A crystalline form of sugar is preferred for many cake mixing procedures as it helps with the dispersion of the recipe fat and the incorporation of air into the mix (BPS, p. 150). Fruited cakes In cakes where a high proportion of dried fruit is added to the mix (e.g., celebration cakes) it has become traditional to use a proportion of brown sugars and syrups in order to add to the colour and flavour profile of the baked product. Biscuits and cookies Commonly the finer grades of sugar, e.g. pulverised, are used in the manufacture of biscuits and cookies. This is because the added water levels are relatively low and so there is a significant potential for sugar re-crystallisation of the surface of the products. In some biscuits brown sugars or syrups may be added to confer colour and flavour. Pastries Caster or pulverised sugar is usually preferred for the manufacture of pastries in order to avoid sugar spotting on the surface of the baked pastries. Other bakery products Icings, toppings and fillings often use a proportion of the finest sugar grades, e.g. icing sugar. If you are not able to access or store a range of sugar types you may have to consider modifying your mixing procedures. For example, with the coarser grades you may have to dissolve the sugar in the recipe water before adding it to the other ingredients. If the sugar levels in your product are high with respect to the water levels you may still have problems with re-crystallisation. References

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2006) Baked Products: Science, Technology and Practice, Blackwell Publishing, Oxford, UK. CAUVAIN, S.P. and YOUNG, L.S. (2008) Bakery Food Manufacture and Quality: Water Control and Effects 2nd edn, Wiley Blackwell, Oxford, UK. WILLIAMS, T. and PULLEN, G. (2007) Functional ingredients. In (eds S.P. Cauvain and L.S. Young) Technology of Breadmaking 2nd edn, Springer Science + Business Media, New York, NY, pp. 51±92. CAUVAIN, S.P.


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3.11 Can you explain some of the main features of alternative sugars to sucrose and how they might be used in baking? The sugars used in baking fall into two main groups classed as mono- and disaccharides. Mono-saccharides are sometimes called `simple' sugars because they consist of one glucose molecule, while the di-saccharides comprise two glucose molecules in different configurations. There are a number of key differences between sucrose and the other sugars that may be used in baking; important ones are related to the impact on the gelatinisation characteristics of wheat starch and therefore product structure, their impacts on product water activity and in turn product shelf-life, and their relative sweetnesses (see Table 8). All sugars contribute to the Maillard browning reaction which forms the crust colour of baked products. The main mono-saccharides are fructose and glucose, both of which occur naturally in fruits. Fructose is an isomer of glucose (that is a glucose molecule with a different arrangement of atoms in the molecule) which can be obtained in the crystalline and liquid forms. It is a sugar which is often used in diabetic products because its initial metabolism in the human digestive system does not require insulin. Fructose may be used in a syrup form (high fructose corn syrup, mainly a mixture of fructose and dextrose) which is readily fermentable by yeast. Glucose may be used as a powder (dextrose monohydrate) or as a syrup (containing about 20%) water with different amounts of dextrose. The percentage of reducing sugars in the syrup is given by its dextrose equivalent (DE). Glucose syrups are found mainly in jams and fondants, though they may find use in cake and biscuit making. Dextrose solids are often used to extend the mould-free shelf-life of cakes but their level of addition is limited by the browning reaction that occurs. The main di-saccharides (in addition to sucrose) are maltose and lactose. Maltose finds its way into baked goods usually as part of malted wheat or barley products and finds use in bread and other fermented goods. It is commonly available in the form of a syrup with a low degree of browning. In its purer, crystalline form maltose has been used to slow down starch retrogradation. Lactose is present in milk products. Its use is limited because of its low solubility. It is a reducing sugar, which explains why the addition of milk powders increases the richness of crust colour in baked products. Lactose may also come as a component of hydrolysed whey products. Table 8 Relative sweetness of sugars Sugar Sucrose Fructose Maltose Lactose Glucose syrup

Relative sweetness 1.0 1.7 0.35 0.27 0.30

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3.12 What are the differences between diastatic and nondiastatic malt powders and how can they be used in baking? Malt flours are most commonly made from wheat, barley and to a lesser extent oats. After the malting process the products of the different cereals have slightly different characteristics but essentially they fall into two categories: diastatic in which a range of enzymes remaining active, and non-diastatic in which the enzymes are inactivated. The malting process is based on the partial germination of the grains. Initially the cleaned grains are `steeped'; that is mixed with a pre-determined quantity of water and stored under conditions which encourage the grains to germinate. After the requisite time, germination is arrested by removing water with the application of gentle heat. The `malt' is mixed with water and a liquor extracted. It is the malt liquor extract which is dried under varying conditions to deliver a range of malt powders with different characteristics. As all enzymes are heat sensitive, the greater the heat input during drying, the lower the enzymic activity which remains in the product. Also the greater the heat input, the darker the malt powder will be. All malt powder products have a slightly sweet, roasted flavour; the degree of flavour intensity varying with the degree of heat treatment used in the preparation. This distinctive malt flavour is carried through to the baked product with the intensity varying according to the grade of malt flour used and its level of addition. Clearly the more malt flour that is added to the product, the more pronounced the flavour will be. If your main interest in using malt is to confer flavour to products, then you can use either the diastatic or non-diastatic forms. The term diastatic activity refers to a suite of different enzymes that are present in the malt flour. The germination process in the grain is based on the conversion of starch to sugars to provide food for the early stages of plant growth. This means that the amylase enzymes, especially alpha-amylase, are a significant component of diastatic malt flours. As is well known, increases in the alpha-amylase levels in dough increase its gas retention properties. However, high levels of cereal alpha-amylase can lead to quality problems such as `keyholing', caving in on the side crust (BPS, pp. 57±8) as well as potential stickiness in the bread crumb and slicing problems (Cauvain and Young, 2006). Other enzymes may be active in the malt powder and these include proteolytic enzymes which can have adverse effects on gluten structures. References

and YOUNG, L.S. (2001) Baking Problems Solved. Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2006) The Chorleywood Bread Process. Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P.


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3.13 We read a lot about the different enzymes that are now available and how they might be used in baking. Can you tell us what they are and what functions they have? There are many different types of enzymes in the natural world and they are an essential part of the natural reactions in life. They may be described as organic or biological catalysts which accelerate the rates of critical reactions in plant and animal systems. They have a similar structure to proteins. They are characterised by the type of reaction that they catalyse and are very specific in action; that is they can only catalyse one specific reaction. All enzymes originate within the cells of which plants and animals are composed. For example, in the bakers' yeast cell are all of the enzymes that it requires to break down sugars and other nutrients for reproduction and growth. Various microorganisms are the main source of industrial enzymes. Specific microorganisms (commonly moulds) are developed under appropriate fermentation systems in a similar manner to that of bakers' yeast (Williams and Pullen, 2007). At the end of reproduction and growth period the cells are disrupted and the cell contents refined to separate out the different specific enzymes that are present. Commercial enzymes are usually of a high purity but most of them will have some residual or `side-effects' associated with other enzymes which are present in the sample. The commercial product is usually too concentrated to be used without being diluted and it is in this diluted form that enzyme preparations are used in the flour mill and bakery. Many ingredients used in baking (e.g., wheat flour, yeast, soya flour, malt flour) are enzymically active. The main groups of enzymes used as èxtra' additions in the manufacture of baked goods are discussed below. However, it is important to recognise that enzymes require suitable conditions for them to work effectively. A suitable moisture level is one of the key requirements and enzyme activity in dry ingredients is low. If the moisture level is low the enzymes remain inactive but when the moisture level increases they can quickly become active. As might be expected for a biochemical reaction, enzyme activity is temperature sensitive with activity gradually increasing as the temperature is increased. All enzymes are eventually inactivated by heat, though thermal inactivation temperatures vary according to the particular enzyme, its source and the environment in which it is being used. In baking most (but not all) enzymes are inactivated by the temperatures achieved in the product during oven heating. Other factors that will affect enzyme activity include the pH (acidity) of the environment in which it used, the availability and condition of the substrate on which it acts and the water activity of the dough or batter. Before discussing the types of enzymes and their application in baking, the question of specificity of action must be considered. As stated above, enzymes are highly specific in their action and this specificity can extend beyond the action of an enzyme on particular substrate to include very specific sites of action within the substrate molecular structure. It is this increasing knowledge of the specificity of enzymes that has partly accounted for the increase in the range of products which are now available for use in baking.

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The addition of enzyme active materials to baked products is highly regulated and in most cases the source of that enzyme is specified. In many parts of the world legislation does not currently require enzymes additions to baked goods to be labelled and they fall into the general category of `processing aids'. Even as processing aids they will have required formal approval for use in the production of food. Amylases These are the best known groups of enzymes used in baking. There are two main types of amylase, known as alpha and beta. Together they are responsible for progressively breaking down starch (a complex carbohydrate composed of glucose chains) into dextrins, high molecular weight sugars and finally to simpler sugars such as maltose (which can be used by bakers' yeast). Both alpha- and beta-amylase are present in wheat flour. The level of alpha-amylase activity varies depending on a number of factors, not least of which is level of moisture in the maturing wheat ears. Beta-amylase is usually abundant in wheat flours but alpha-amylase levels may be low and so it is a common practice to augment its level through the addition of a suitable enzyme active material in the flour mill (Cauvain and Young, 2009). The measure of cereal alpha-amylase activity in wheat flour is measured using the Hagberg Falling Number test (BPS, p. 24). This description of the action of amylases is simplistic. Starch granules in flour are made up of two components: amylose a straight chained molecule and amylopectin a branched molecule. The action of alpha-amylase is commonly described as random with respect to the amylose and amylopectin molecules while that of the beta form is more specific and it cleaves relatively small molecules from the starch components (Williams and Pullen, 2007). Thus, the combined action of the two forms of amylase is critical in the use of amylase enzymes as bread improver. A key function of alpha-amylase in bread production is to improve dough gas retention and in consequence bread volume and softness (Cauvain and Chamberlain, 1988). The source of the alpha-amylase has a significant impact on the overall effect (BPS, pp. 59±60; Kulp, 1993; Williams and Pullen, 2007). Some forms of amylase are known to have anti-staling effects in bread. This arises from the generation of high molecular weight sugars which penetrate the starch granules helix structure and inhibit the re-crystallisation process after baking (see 3.14). Hemicellulases The action of hemicellulases is on plant cell-wall materials ± hemicellulose. The endosperm of wheat is composed of small cells which hold the starch, protein and lipids. The cell walls are composed of the large polymers mainly based on the sugar xylose. Hemicellulases (sometimes referred to as xylanases) act on the cell walls to break the material down into mainly xylose and arabinose. The net result of the addition of hemicellulase is to increase dough gas retention and to affect dough water absorption capacity. The effect of this group of enzymes is


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complex and the impact on dough water absorption capacity may be negative in some dough-making situations, with the addition of the enzyme causing an increase in dough stickiness. Lipases The addition of lipases has been shown to improve dough gas retention and bread volume. Their action is on triglycerides (fats, lipids) and the breakdown products of that action are in order: di-glycerides, mono-glycerides and finally fatty acids. The mono-glycerides formed from the action of lipase in dough are known to contribute anti-staling properties in bread and so it is seen as a potential replacement for emulsifiers in bread recipes (Rittig, 2005). Proteolytic enzymes This group of enzymes include proteases and proteinases and their action is on the gluten network formed in the dough. They are usually added to `weaken' the dough system and are sometimes used in biscuit production. They reduce dough gas retention and modify dough rheology making it softer and more readily processable (Kulp, 1993). They should be used with great care, if at all in breadmaking. Oxidases Glucose oxidase enzymes are sometimes used in bread making. In the presence of oxygen, they catalyse the oxidation of the beta form of glucose and in so doing produce hydrogen peroxide. The ability of the hydrogen peroxide generated in the dough to aid the formation of the disulphide bonds is said to be the basis of the improvement in dough gas retention (Vemulapalli et al., 1998). References

and CHAMBERLAIN, N. (1988) The bread improving effect of fungal alphaamylase. Journal of Cereal Science, 8, Nov., 239±248. CAUVAIN, S.P. and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2009) The ICC Handbook of cereals, flour, dough and product testing: Methods and Applicationss, DEStech Publishing, Lancaster, NJ. KULP, K. (1993) Enzymes as dough improvers. In (eds B.S. Kamel and C.E. Stauffer) Advances in Baking Technology, Blackie Academic & Professional, Glasgow, UK, pp. 152±178. RITTIG, F.T. (2005) Lipopan F BG ± unlocking the natural strengthening potential in dough. In (eds S.P. Cauvain, S.E. Salmon and L.S. Young) Using Cereal Science and Technology for the Benefit of Consumers, Woodhead Publishing Ltd, Cambridge, UK, pp. 147±151. VEMULAPALLI, V., MILLER, R.A. and HOSENEY, R.D. (1998) Glucose oxidase in breadmaking systems. Cereal Chemistry, 75, 439±442. WILLIAMS, T. and PULLEN, G. (2007) Functional ingredients. In (eds S.P. Cauvain and L.S. Young) Technology of Breadmaking 2nd edn, Springer Science + Business Media LLC, New York, NY, pp. 51±92). CAUVAIN, S.P.

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3.14 How do anti-staling enzymes work? Can they be used in cake as well as in bread and fermented products? There has been significant interest in using enzymes as anti-staling agents to augment the effect of emulsifiers or to replace them. When we refer to staling it is in the context of slowing down the firming of bread and cake crumb which comes from the retrogradation of starch during storage. This is in contrast to the increased softness which can be obtained by higher moisture levels in the baked product or through the increase of product volume (the latter is commonly a result of adding enzymes to bread formulations). There are two main groups of enzymes with anti-staling effects in baked goods and these are specific types of alpha-amylase and lipase; as is well known the former acts on damaged wheat starch breaking it down progressively to maltose, while the latter acts on triglycerides to eventually yield fatty acids. The starch polymer consists of a series of sugar molecules linked together as linear chains of amylose and branched amylopectin structures. Alpha-amylase is able to cut through these linkages at different but very specific points, depending on the types of amylase, to yield different sugars of varying molecular weights. Sugars are known to function as anti-staling ingredients in starch-based foods, probably by raising the glass transition temperature (see 9.7) and suppressing the re-crystallisation of the amylopectin (the main starch component responsible for staling in bread). In the case of lipase the specific action is to generate mono-glycerides in situ in the dough and mono-glycerides are proven anti-staling agents in bread. Again the specific type of lipase will dictate which specific mono-glyceride is generated and at what rate and level in the bread dough. The anti-staling effect of some enzymes is now well established in bread. In cakes it is less well established. Since the action of the specific anti-staling alpha-amylases is based on the production of a variety of sugars, it is difficult to see why this should be of significant benefit in cakes, which by virtue of their formulation already contain high levels of sugars. There is some evidence that supports increased softness values for cake crumb containing specific lipases. This is perhaps more understandable because of the generation of the monoglyceride which is known to have crumb softening effects in cake making. It is likely that any observable anti-staling effects of enzymes will depend heavily on the type of cake being produced and is more likely to be observed in low-fat cakes, such as sponge, or low-ratio cakes where the levels of sugar are lower.


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3.15 Can you explain the different terms used to describe bakery fats? What are the functionalities of the different forms in baking? Chemically all fats and oils consist of atoms of carbon (C) hydrogen (H) and Oxygen (O). They have the same basic structure which consists of a molecule of glycerol combined with up to three fatty acids. The basic nomenclature is mono-, di- and tri-glyceride according to whether 1, 2 or 3 fatty acids are attached to the glycerol molecule. The term oil is used to describe a fat in its liquid form. All fats become oils if the temperature is raised high enough and all oils become solid fat if the temperature is sufficiently reduced. The term oil is most commonly used for fats which exist as liquids at temperatures around 15±25ëC. Fats used in bakery practice are commonly a mixture of liquid and solid fat components and this may be expressed as the melting profile or solid fat index of the fat concerned (BPS, pp. 38±40). Fatty acids are one of the key building blocks of animal and plant tissues. There are different fatty acids and their physical and chemical form varies according to their chain length and absence/presence of carbon double bonds (C=C) in the chain. The significant impact of the different fatty acids is on the melting point of the fat and this determines whether the fat is solid or liquid at a given temperature. The degree of saturation in fats describes the number of carbon double bonds which are present. As the number of carbon double bonds increases, the degree of saturation decreases and so does the melting point of the fat; the downwards progression is from saturated to mono-unsaturated to poly-unsaturated so that highly saturated fatty acids tend to be solid. Saturated fats tend to be very stable and have a long shelf-life. They also tend to have highly functional roles in the manufacture of baked products; such as improving the gas retention properties of bread dough (Williams and Pullen, 2007), aid air incorporation in cake making (BPS, p. 150) and provide lift in laminated products (BPS, pp. 124±5). However, they also tend to have a negative health image. The proportion of the different forms of saturation varies according to the source of the oil/fat. Today there has been a significant move away from animal fats in bakery products (with the possible exception of butter) to vegetable-based fats, because many of them are low in saturated fats. However, this means they are also mainly in the liquid form and so do not have the baking functionality of the solid fats. The main exception is palm oil which is about 50% saturated and 40% mono-unsaturated fat. It is possible to modify the physical and chemical characteristics of natural oils. One method is hydrogenation, in which the oil is reacted with hydrogen gas at high temperatures and pressure. The process converts poly-unsaturates to mono-unsaturates and then to saturates and increases the functionality of the fat for different baking processes. The process of hydrogenation produces saturated fats but no significant levels of trans fats.

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However, partial hydrogenation, which had become more popular because of concerns over the consumption of saturated fats, generates significant levels of trans fats. While these fats retain functionality for baking, their `healthiness' in the diet has been questioned. The process of partial hydrogenation produces different levels of trans fats from different types of fat. The trans form of fat exists because there are two physical ways for a fat to form with the same combination of CHO atoms; the trans is one form and the other is known as the cis form. Trans fats do occur in nature and are present in products such as butter, milk and eggs. There are alternative ways to hydrogenation for providing baking fats with the functionality necessary for baking. Oils from natural sources, for example palm oil as discussed above, are a mixture of solid and liquid fractions and so the physical separation of the different fractions can be used to prepare a range of different fats with specific functional properties. Using this technique it is possible to prepare stearine oil fractions with melting points of up to 60ëC. The process is referred to as fractionation and has also been applied to butter to provide specific fractions which are better suited to processing at higher temperatures. Interesterification involves enzyme (lipase)-assisted modification of the oil or fat composition. Any oil or fat combination can be interesterified. Solid fats may exist in a number of crystalline forms depending on how they have been prepared in commercial practice. It is largely the cooling of liquid fats which determines the crystalline form, though the form may change during subsequent storage. It is said that fats exhibit polymorphism and the three crystalline forms are denoted as , 0 and . The crystals have the lowest melting point and are small, unstable crystals. The transition is from to 0 and then to ; the latter form tend to be the largest crystals and have the highest melting points. The crystalline forms of the fats have been linked with their functionality in baking (e.g., Cauvain, 2001). References

(2001) The production of laminated products. CCFRA Review No. 25, Campden-BRI, Chipping Campden, UK. CAUVAIN, S.P. and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. WILLIAMS, T. and PULLEN, G. (2007) Functional Ingredients. In (eds. S.P. Cauvain and L.S. Young) Technology of Breadmaking 2nd edn, Springer Business+Science Media, LLC, New York, NY, pp. 51±92. CAUVAIN, S.P.

Further reading

(1993) Fats and fat replacers. In (eds. B.S. Kamel and C.E. Stauffer) Advances in Baking Technology, Blackie Academic and Professional, Glasgow, UK, pp. 336±370. STREET, C.A. (1991) Flour Confectionery Manufacture, Blackie and Son Ltd, Glasgow, UK. STAUFFER, F.E.


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3.16 We want to make a range of bakery products using butter as the main or only fat in the recipe. Can you advise us of any special technical issues that we need to take into account when using butter? The composition of butter is usually fixed by local regulations. It is an emulsion of water-in-oil and typically contains more than 80% fat, less than 2% milk solids and less than 16% water. Despite having a fixed composition its performance in baking can vary. The best known variation comes with the twice yearly change in the feeding patterns for cows in many parts of the world (Rajah, 1997). With the change of feed come small but important changes in the underlying fatty acid composition and solid fat content, which can affect its ability to incorporate air during creaming processes in the manufacture of baked products (e.g., cakes and biscuits). Butter contains significant amounts of butyric acid (a low molecular weight fatty acid), which is volatile and makes a significant contribution to the flavour of the fat. The release of traces of this acid through the process of hydrolysis makes butter particularly susceptible to rancidity. To avoid any potential problems the butter will be delivered chilled and should be stored at the same temperature, typically around 4±6ëC. You should always use the butter within its designated shelf-life and you will find it helpful to set up a strict stock rotation system. The solid fat content of butter (BPS, pp. 37±40) at different temperatures is given in Table 9. The data highlight some of the technical problems with using butter. Because the solid fat content is very high at low temperatures, it cannot be used straight from the refrigerator but must have its temperature raised before it can be used. This `tempering' process takes time and requires careful control to ensure uniformity of processing performance (see also 3.17). Achieving the optimum processing temperatures with butter is very important for its effective use. For examples of relevant processing temperatures for laminated pastry products see 7.6. The solids content of butter is lower than normally considered suitable for cake making and there is a tendency for àll-butter' cakes to lack volume. Adding a suitable emulsifier to the recipe (e.g., glycerol mono-stearate) commonly solves the problem (BPS, p. 47). Table 9 The solid fat content of butter at different temperatures Temperature (ëC) Solid fat (%)

References

5 53

10 48

15 35

20 24

25 17

30 10

35 7

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. RAJAH, K.K. (1997) Cream, butter and milk products. In (ed. A.J. Bent) The Technology of Cake Making, Blackie Academic & Professional, London, UK, pp. 48±80. CAUVAIN, S.P.

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3.17 We are using butter in several of our bakery products which comes in chilled at about 4ëC (as cartons on pallets) and are encountering problems with variability in its processing. We recognise that it is likely to be associated with the temperature of the butter when we are using it. What is the best way to treat the butter in order to get a more consistent performance? In order to get a consistent processing and baking performance from butter you need to use it at temperatures between 14 and 20ëC, depending on the product. In the manufacture of cake batters and creams the butter plays a major role in the necessary air incorporation and so must be sufficiently plastic at the time of mixing; temperatures at the higher end of the above range are most suitable in such cases. For pastry making, temperatures towards the lower end of the range may be used but a significant degree of plasticity is still required (see 7.6). As your butter is arriving in the chilled form, you will need to raise its temperature by quite a few degrees before it is in its optimum temperature range. The best way to raise the butter temperature is to store it in warm environment, for example at temperatures between 20 and 25ëC (no more than 30ëC) but to obtain consistent performance it is crucial that the temperature of the whole carton reaches these temperatures. To achieve this you will need to make sure that there is sufficient air circulation around each carton and that you allow sufficient time for equilibration of the carton temperature to occur. The whole process can take several days and we suggest that you allow at least 4±8 days' equilibration before trying to use the butter. Do not be tempted to use high air temperatures to `speed-up' the process, as this can lead to significant òiling' on the surfaces of the butter in the cartons and loss of functionality. Butter that has oiled and then cooled ends up with a different (larger) crystal structure, which makes it unsuitable for the manufacture of most bakery products. Radio-frequency heating and microwave have been suggested and used for tempering butter. This can reduce, but not replace, the storage time. Once again oiling of the butter should be avoided. In the manufacturing process the butter may well be pumped or extruded before use. The mechanical action that these processes involve helps in achieving a more uniform temperature distribution throughout the fat but should not be used to try and replace sound tempering procedures.


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3.18 What are the differences between dough conditioners and bread improvers? What consideration should we take into account when choosing which one to use? There is no precise definition of these terms. It could be argued that the term dough conditioner could include the use of materials to modify any dough-based product, which would include bread, biscuit and pastry doughs, while the term `bread improver' suggest that any effects are confined exclusively to bread and fermented products. However, in practice both terms are commonly used interchangeably and this can create some confusion. Both terms are used to describe a functional ingredient or a mixture of functional ingredients that are added at low levels in order to beneficially modify one or more characteristics of the final qualities of bread and fermented products or their processing intermediaries, i.e. the dough. All of the ingredients that would fall into this category will modify final product qualities and the vast majority will also modify the rheological properties of the dough. In a number of cases it is modification of the dough rheology that delivers the improvement to the final product. The compositions of dough conditioners and bread improvers are complicated and varied according to the particular bread product being made and processes used to make them. They may also vary with time as the formulations are adapted to changing raw material inputs, such as any changes in wheat and flour quality from one harvest year to the next, and to legislative and consumer pressures. When you are considering which dough conditioner or bread improver to use, you should consider first what quality changes you wish to effect and then identify which functional ingredient will deliver those quality changes that you are seeking. Examples of improvement categories and the functional ingredients that contribute to those improvements include: · Improved dough processing ± enzymes and reducing agents (e.g., L-cysteine hydrochloride, see 3.21). · Improved product volume ± oxidants (e.g., ascorbic acid), emulsifiers, enzymes. · Improved cell structure ± oxidants. · Improved crumb softness ± emulsifiers, enzymes. · Extended product shelf-life ± emulsifiers, enzymes. · Increased mould-free shelf-life ± preservatives. The individual ingredients that you will be able to choose from will be governed by local legislation and you should check carefully as to what is permitted for your country.

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3.19

What is lecithin and how is it used in baking?

Lecithin is a naturally occurring emulsifier found in animal and vegetable products such as milk, eggs (in the yolks) and soya beans, now the major source of the material. It is a liquid at temperatures around 20ëC and is soluble in oil. Purified and modified forms are available as a plastic liquid and in powder form (often blended with another food grade powder for ease of handling). The main constituent of lecithin in terms of its functionality is a mixture of phospholipids, with the combination of the different types being specific to its animal or plant source. As a component of egg yolk, lecithin plays a role in helping to stabilise the air bubbles that are mixed in during the preparation of cake batters. This role is especially important in the preparation of sponge products, which tend to have low levels of added fat. The lecithin phospholipids are part of the egg lipoproteins that are found at the interface of the air with the aqueous phase in cake batters and aid bubble stability at the time in the oven when the cake batter system changes from a water-in-oil to oil-in-water emulsion. Lecithin is often used along with other emulsifiers, such as glycerol mono-stearate, in sponge cake making. The addition of lecithin at low levels in the manufacture of cake doughnuts is said to reduce fat absorption during frying and to confer tenderness to the final product eating qualities. Lecithin may be used in the manufacture of some bread types. It enhances gas retention in the dough to a degree but less so than other more commonly used emulsifiers. In crusty breads it tends to give a thicker, denser crust, which retains its crispness for longer periods of time (Williams and Pullen, 2007). In biscuits, lecithin may be used as a means of reducing fat levels by up to 10% without adversely affecting biscuit quality. Dissolving the lecithin in fat makes it easier to handle (Manley, 2000) and it may help with the dispersion of the fat throughout the dough, giving it a smoother feel. In higher sugar cookies the addition of lecithin helps with the restriction of flow during baking. In the bakery low levels of lecithin (around 5%) are often found as a component of oil-based pan-greasing agents. References

(2000) Technology of biscuits, crackers and cookies, 3rd edn, Woodhead Publishing Ltd, Cambridge, UK. WILLIAMS, T. and PULLEN, G. (2007) Functional ingredients. In (eds S.P. Cauvain and L.S. Young) Technology of Breadmaking 2nd edn, Springer Science + Business Media, LLC, New York, NY, pp. 51±92. MANLEY, D.

Further reading

(1993) Lecithin and phospholipids in baked goods. In (eds B.S. Kamel and C.E. Stauffer) Advances in Baking Technology, Blackie Academic & Professional, Glasgow, UK, pp. 223±253.

SILVA, R.


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3.20 What is meant by the term `double-acting' baking powder and what is the value of using such products? Double-acting baking powders usually comprise a mixture of at least two baking acids and sodium bicarbonate. The overall composition of the baking powder will be balanced taking into account the neutralising value of both acids with respect to the sodium bicarbonate. Each of the acids will have a different rate of reaction (ROR) (see 2.11) and the intention is to spread and control the release of carbon dioxide gas over an extended period of time. Double-acting baking powders are most commonly used in the manufacture of cakes and are especially useful in the delivery of carbon dioxide production in the oven, which helps give cakes extra volume ± almost the cake equivalent of oven spring in bread. The process is shown schematically in Fig. 15. The level of sugars used in the manufacture of cake batters delays the gelatinisation of the wheat starch ± the main structure forming agent. This means that cake batters are fluid until relatively late on in the baking process. While the batter is fluid it is capable of expansion. With many of the faster-acting baking acids the release of carbon dioxide is mostly completed during mixing and the first few moments of baking, which may lead to a restriction of cake volume and a tendency for the products to have a peaked shape. This is commonly overcome by increasing the level of addition. An advantage of using a double-acting baking powder is that the flavour of the residual salt in the baked cake can be modified by using different baking acids. It is also possible to aid sodium reduction in baked products without unduly compromising product quality by using two different types of acids in the baking powder.

Fig. 15 The release of carbon dioxide from double-acting baking powder in cake baking.

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3.21 We have been having some problems with the quality of our bread, pastries and biscuits, and one solution that has been recommended to us is that we should add a reducing agent to our recipes. Can you tell us more about reducing agents and how they function in baked products? We should first start by defining what we mean by reduction. In chemical terms it is used to describe reactions in which hydrogen is added to an element or compound, or in which oxygen is removed from a compound. It is the opposite of oxidation. While both terms are used empirically to cover a number of similar reactions, in baking the reduction and oxidation reactions that take place are very close to the formal definition. A key reaction during mixing is the formation of disulphide bonds between the protein chains in the dough (Stauffer, 2007). Their formation is promoted by oxidation and they contribute to the elasticity of dough. The origins of this property are associated with the ratio of glutenin to gliadin proteins in the wheat flour, though oxidation processes that occur during dough mixing also make a contribution. If the dough is too elastic after mixing, then it may be difficult to process and it is common to consider adding a reducing agent to reduce the number of disulphide bonds that have been formed. A commonly used reducing agent in the preparation of fermented dough is Lcysteine, a naturally occurring amino acid used in the hydrochloride form to improve its solubility. The addition of L-cysteine hydrochloride is often recommended to reduce the level of work input required for the manufacture of bread by the Chorleywood Bread Process when using very strong flours or encountering difficulties with dough moulding. This approach should only be used when there is no alternative, more suitable flour available as the results of using L-cysteine hydrochloride are often equivocal. The addition of L-cysteine hydrochloride has been shown to be beneficial in the manufacture of other fermented products and has become a common ingredient in dough conditioner and improvers added in the production of rolls, pizza bases (Williams and Pullen, 2007) and hamburger buns. With all of these bakery products the main effect of the L-cysteine hydrochloride is to reduce the elasticity of the dough and to assist in achieving the desired shape without causing undue damage to the dough pieces during moulding. L-cysteine hydrochloride also finds potential use in the manufacture of short and laminated pastes to improve the blocking and sheeting processes involved. The gluten structure is less well developed in short pastry making than with laminated pastes but both can benefit from the addition of a reducing agent. In pastry making an alternative to the addition of L-cysteine hydrochloride is sodium metabisulphite. Both of these reducing agents need to be used with care in the manufacture of pastry products because the re-cycling of trimmings can lead to their progressively increasing concentration in the recipes being used with subsequent excessive softening of the paste. Long delays in paste


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processing can also lead to excessive softening of the paste when reducing agents are present in the recipe. Sodium metabisulphite has found use as a reducing agent in the manufacture of biscuits, especially the low-fat, low-sugar types embraced by the generic term `semi-sweet'. The level of gluten development occurring during the mixing of semi-sweet biscuit dough is considerably less than that achieved in bread dough mixing but with stronger flours it is still sufficient to contribute to biscuit shrinkage. This shrinkage may be seen during the sheeting processes but is commonly seen when the biscuit units have been cut from the sheet. In severe cases the shrinkage is immediately after cutting while in less severe cases it may only be observed as shrinkage after the biscuit has been baked. In this case the biscuit dimensions will differ from those used in cutting and round biscuit shapes commonly develop eccentricity. The use of sodium metabisulphite is not universally accepted (Manley, 2000) and common àdditive-free' approaches are to more closely specify the qualities of the flour to be used or to add more water during dough mixing to yield a less elastic gluten network. The concern over the addition of chemical reducing agents has led to consideration of more `natural' forms. Bakers' yeast cells are a rich source of the natural reducing agent glutathione (Bonjean and Guillaume, 2003). In scratch bread making the yeast cells are intact and the glutathione has no direct contact with the dough proteins. However, if the yeast cell membrane is damaged then there is potential for the glutathione to react with the protein network. Freezing yeast and yeasted doughs leads to irreparable damage to the cell membrane, and the effect of the glutathione is undoubtedly one of the contributing factors to the loss of gas retention in frozen bread dough. Commercial extracts of yeast cell contents are available for use as a reducing agent. Glutathione (and L-cysteine hydrochloride) may be used in the manufacture of pasta to denature the gluten in the dough (Kent and Evers, 1994). Glutathione occurs naturally in flour. It is among the low molecular weight thiol compounds, though the amounts present in flour are small. Low molecular weight thiols diffuse rapidly through the dough and so despite their low concentrations they are likely to be active in affecting the rheological properties of the dough. In some instances changes in glutathione level have been linked with the `freshness' of flour and its performance in baking (Chen and Schofield, 1996). Glutathione levels do vary with wheat type and the ash content of the flour (Sarwin et al., 1992). The content of low molecular weight thiols (including glutathione) is known to be affected by oxygen, probably during the milling of wheat to flour and almost certainly during dough mixing. Kieffer et al. (1990) found that dough resistance fell and flour extensibility increased as the level of glutathione increased. No discussion of the use of reducing agents in baking is complete without including some discussion of the role of ascorbic acid. Chemically ascorbic acid is a reducing agent but its conversion to dehydro-ascorbic acid is responsible for its oxidising effects in breadmaking (Williams and Pullen, 2007). The

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availability of oxygen for the conversion is crucial in this context but, as has been shown, oxygen depletion can occur quite quickly in bread dough (Cauvain and Young, 2006). This suggests that in the anaerobic environment in the dough, which is attained after mixing the ascorbic acid present, has the potential to act as a reducing agent, and practical experiments show that if ascorbic acid is present in fermenting dough, then there can be loss of bread volume (see 4.21). However, if the dough is re-mixed (e.g., as during knock-back, see 4.26) then the re-introduction of oxygen allows for some further oxidation effect from the ascorbic acid. References

and GUILLAUME, L-D. (2003) Yeast in bread and baking products. In (eds T. Boekhout and V. Robert) Yeasts in Food, Woodhead Publishing Ltd, Cambridge, UK, pp. 289-308. CAUVAIN, S.P. and YOUNG, L.S. (2006) The Chorleywood Bread Process, Woodhead Publishing Ltd, Cambridge, UK. CHEN, X. and SCHOFIELD, J.D. (1996) Changes in glutathione content and breadmaking performance of white flour during short-term storage. Cereal Chemistry, 73, 1±4. KENT, N.L. and EVERS, A.D. (1994) Technology of cereals 4th edn, Elsevier Science Ltd, Oxford, UK. KIEFFER, R., KIM, J-J, WALTHER, C., LASKAWY, G. and GROSCH, W. (1990) Influence of glutathione and cysteine on the improving effect of ascorbic acid stereoisomers. Journal Cereal Science, 11, 143±152. MANLEY, D. (2000) Technology of biscuits, crackers and cookies 3rd edn, Woodhead Publishing Ltd, Cambridge, UK. SARWIN, R., WALTHER, C., LASKAWY, G., BUTZ, B. and GROSCH, W. (1992) Determination of free reduced and total glutathione in wheat flour by an isotope dilution assay. Z Lebensm Unters Forsch, 195, 27±32. STAUFFER, C.E. (2007) Principles of dough formation. In (eds S.P. Cauvain and L.S. Young) Technology of Breadmaking 2nd edn, Springer Science + Business Media, LLC, New York, NY, pp. 299±332. WILLIAMS, T. and PULLEN, G. (2007) Functional ingredients. In (eds S.P. Cauvain and L.S. Young) Technology of Breadmaking 2nd edn, Springer Science + Business Media, LLC, New York, NY, pp. 51±92. BONJEAN, B.

Further reading

and BRUMMER, J. (1995) Frozen & Refrigerated Doughs and Batters, AACC, St. Paul, MN. WEISER, H. (2003) The use of redox agents. In (ed S.P. Cauvain) Bread Making: Improving Quality, Woodhead Publishing Ltd, Cambridge, UK, pp. 424±446. KULP, K., LORENZ, K.

4 Bread and fermented products

4.1 What characteristics should we specify for white bread flour and why? The breadmaking potential of flour is strongly influenced by the proteins present in the wheat. There proteins hydrate and, with the input of energy during mixing, form the gluten network which provides much of the gas-retaining properties of bread dough. However, there are other flour properties that should be taken into account when deciding on a particular flour specification and there are process factors to consider, such as which breadmaking process you are using and what type of product you are making. As a guide you should consider the following as a minimum for white flour: · Protein content ± around 13% on a dry matter basis. This figure should increase by about 1% if you are using a process which uses bulk fermentation to mature the dough before processing or if you are making `free-standing', hearth- or oven-bottom type breads. As a general rule the higher the protein level in the flour, the greater its gas retention potential and therefore the greater the resultant bread volume and crumb softness. · A measure of the `purity' of the white flour; that is the level of bran particles which are present. This is often measured as ash or grade colour figure (see 2.1 and 2.2). The presence of bran has a negative impact; the higher the level of bran present, the poorer the gas retention of the dough. · The water absorption capacity of the flour, since this is an indicator of how much water will need to be added at the dough making. A number of different factors affect the water absorption capacity (see BPS, pp. 25±6). The measured water absorption capacity is only a guide as to the level that will be used in the bakery. It is usual for the actual level of water added to dough to

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be reduced when making free-standing breads, as this helps the dough to retain the required product shape during processing (Cauvain and Young, 2008). · Hagberg Falling Number ± typically this should be above 250 seconds (see BPS, p. 24). · Protein quality ± this is usually assessed by measuring the rheological properties of a flour-water dough. In general the flour should possess reasonable resistance to mixing or stretching, sufficient extensibility and good stability. There are a number of different tests which can give you this information. For a summary of the methods see BPS, pp. 21±2, and for more detailed information see Cauvain and Young (2009). · Flour treatments and additives ± ideally the flour should be untreated but if this is not possible any additions should be kept to a minimum. Common additions are ascorbic acid as a bread ìmprover' and alpha-amylase. If you are using a bread-making process in which the flour would benefit from the addition of bread improvers, it would be better to add them in the bakery as part of the recipe. Any additions to the flour should be discussed with your miller supplier. References

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2008) Bakery Food Manufacture and Quality: Water Control & Effects, Wiley-Blackwell, Oxford, UK. CAUVAIN, S.P. and YOUNG, L.S. (2009) The ICC Handbook of Cereals, Flour, Dough and Product Testing: Methods and Applications, DEStech Publications, Lancaster, PA. CAUVAIN, S.P.

Bread and fermented products

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4.2 We make crusty breads in a retail store and recently we have been having complaints about our products going soft quickly. We have not changed our recipe or process. Can you help us understand what has happened? Your problem was not related to baking but to your cooling and wrapping practices. You had recognised that crusty products should not be stored in impermeable films or plastic bags. If the products are too warm when they are placed in plastic bags then the loss of moisture from the product crumb results in condensation and the condensing moisture is absorbed by the crust turning it soft. It will also increase the risk of accelerated mould growth as the normally low moisture and water activity of the crust both increase. Even when products are adequately cooled before they are placed in impermeable plastic bags, the process of moisture migration from the product crumb to the atmosphere in the bag will occur. This is because the cell network in the bread crumb is open ± referred to as a `sponge' by cereal scientists ± and water can readily escape to the atmosphere. The relative humidity of the atmosphere is lower than that inside the loaf and so the driving force is for moisture to be lost from the crumb. Moisture migration will continue until equilibrium is reached in the bag, that is, the air, the product crust and the crumb all have the same moisture content. If this did happen before the loaf was consumed, the crust would be softer and the crumb drier than normally expected. The rate at which this would occur depends on many factors, not least the temperature at which the product is kept. It has become common practice with many crusty-style products to wrap them in `perforated' film or bags. The material used for the bag has a number of small diameter holes through which moisture can escape. This means that the equilibrium referred to above cannot occur. The positive benefit of this approach is that the moisture differential between crust and crumb is maintained and some of the original product crustiness is maintained. A disadvantage of this approach is that the product crumb will become drier faster than would be the case with an impermeable plastic bag. In fact your problem arose because of a subtle change in the type of perforated film that you were using. Feedback from the check-out staff in the store had indicated that bits of crust were contaminating the scanner and so you changed to a film with smaller diameter perforations. Doing this reduced the scanner problem but also reduced the rate at which moisture was lost from the product, in effect the system behaved more like an impermeable bag and the crust softened more rapidly. The way to reduce the scanner problem is certainly to reduce the perforation diameter but you need to increase the number of perforations per unit area of film so that the moisture vapour transpiration rates (see 9.9) of the two films are equal. The smaller diameter perforations will reduce the size of the crust particles which fall through and the increase in the numbers will maintain the loss of moisture at a level similar to that which you were getting before.

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4.3 We are not a large bakery but are planning to part bake and freeze bread products for bake-off at some later time. What points should we be aware of? The bake-off of frozen bread products gives bakers flexibility of supply to their customers. However, in freezing and baking-off such products it is important that they lose as little moisture as possible in order to reduce the rate at which the final baked product will firm (stale). When cooling the products after their first baking, the core temperature should be checked. A temperature of 30ëC should be aimed for in order to reduce the thermal shock that the products will experience when transferred to the freezer. It takes some time for heat to be drawn out from the product centre while the surface will freeze very quickly. It is better to cool the bread to ambient temperature in the bakery rather than put hot bread in the freezer. Covering the products can help to reduce moisture losses but ensure that you do not get condensation on the product as this will affect the final crust quality. You will get best results if you are able to use a blast freezer rather than a chest-type freezer. The speed of the air movement in a blast freezer can remove as much as 2±3% moisture from the product. To limit moisture losses, keep the freezing times as short as possible. Product core temperatures after freezing should be in the order of ÿ10ëC but remember that products with different dimensions (particular diameter or thickness) will freeze at different rates. Consider collating racks before loading and unloading the freezer ± i.e., fewer door openings ± or fitting an àir' curtain. Opening the blast freezer door reduces its efficiency, which means that the product takes longer to freeze and loses more moisture. Once the products are frozen you should get them into moistureimpermeable bags and into a storage freezer as quickly as possible to avoid moisture losses. The salt in the bread depresses the freezing point to around ÿ4 to ÿ6ëC and so once the temperature rises above this (for example, during packing) the product begins to defrost. Partial defrosting and then re-freezing results in `freezer burn'; this shows as white patches in the crumb which are hard to the touch and have a harsh mouthfeel (BPS, pp. 108±9; Cauvain and Young, 2008). The physical and chemical changes that have occurred in the crumb are not usually reversible so you need to take care of your storage conditions if you are to avoid this problem. Another common problem with frozen bake-off products is that called `shelling' in which the crust of the product detaches from the crumb (Fig. 16). This phenomenon arises because the different moisture content of the crust and crumb cause the two components to freeze and defrost at different rates, which strains the physical links between the two. The problem can occur at a number of stages of the bake-off process depending on its severity: · During frozen storage, especially if the product is stored for long periods of time. · On defrosting before second baking. · After second baking.


Fig. 16

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Shelling of bakery problems.

With prolonged storage times you may see a combination of shelling and freezer burn. In preparing the product for bake-off, check the core temperature on defrosting in ambient conditions. Aim for a temperature of ÿ5ëC (just defrosted). At bake-off consider using higher temperatures than for standard baking with shorter bake times. Moisture loss during second bake depends more on time than on temperature and so accurate timing of bake-off is essential if the product is not to lose too much moisture. Bake-off products will always stale faster than scratch products and excess loss of moisture (either in the freezing or the baking off) will exacerbate this staling (see 4.4). References

and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2008) Bakery Food Manufacture and Quality; Water Control and Effects 2nd edn, Wiley-Blackwell, Oxford, UK. CAUVAIN, S.P.

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4.4 When we re-heat par-baked products we find that they remain soft for only a short period of time, typically an hour or so, but they quickly go hard and become inedible. If we do not re-heat them we find that par-baked products can stay fresh for several days. What causes the change in the rate of firming? Is it the additional moisture lost on the second bake? Your assumption is partly correct. Moisture will be lost from the products at both baking stages and it is more than likely that the sum of the two moisture losses will exceed that of a single bake. The lower the moisture content of the product the firmer the crumb. However, in order to fully answer your question we need to consider the process that cereal scientists call staling. Bread crumb firmness increases during storage even when no moisture is lost from the product. Schoch and French (1947) proposed the most commonly accepted models for bread staling. Their model for bread staling was based on the changes in the two major fractions of the starch in wheat flour, the amylose and the amylopectin, post-baking and during storage. Raw starch granules in flour have an ordered or crystalline structure and during dough mixing those which have been physically damaged during flour milling become hydrated. In the dough entering oven the starch first swells and then later gelatinises as the temperature increases to around 60±65ëC. Gelatinisation disrupts the crystalline structure and the amylose diffuses into the aqueous phase to form an insoluble gel which contributes to a soft crumb structure. On leaving the oven the bread cools and the amylose fraction quickly reassociates; this process gives bread crumb its initial firmness. The other starch fraction, the amylopectin, takes much longer to re-associate, usually several days. It is the process which is responsible for crumb firming during prolonged storage and is the one most commonly associated with bread staling. If stale bread is re-heated it is possible to reverse the amylopectin recrystallisation process and soften the crumb. However, when the breads cools the second time there is a noticeable increase in the rate at which it goes firm; what used to take days now takes a few hours. This increased staling rate is associated with the temperature that the product achieves during re-heating. It is essential to melt all of the amylopectin fraction in the product, which means that the centre crumb temperature should reach 65ëC. If this does not happen then a few unmelted crystals of amylopectin act as seed for the recrystallisation process, which proceeds much faster as a result. Many users are cautious about re-heating bake-off products and are concerned to avoid excess surface colour, consequently the crumb does not reach the critical temperature and re-firming rates can be rapid. Reference

and FRENCH, D. (1947) Studies in bread staling. 1. Role of starch. Cereal Chemistry, 24, 231±249.

SCHOCH, T.J.


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4.5 We have been freezing some of our bread products in order to have products available in times of peak demand. We notice that there is `snow' or ìce' in the bags when we remove them from the freezer. Can you tell us why this happens and how it can be avoided? Freezing products ready to meet peaks in customer demand is a common practice. Bread and rolls, if wrapped to prevent any moisture losses, will keep well in the frozen state. Bread products have a high moisture content and a high water activity. Once frozen, the products should be stored below their Tg (glass transition temperature) (see 9.7). Effectively this is the temperature at which all the soluble materials in the product become immobile or frozen. It has been estimated that approximately 30% of the water in bread remains unfrozen even at the usual storage temperature of ÿ20ëC. If the temperature of the frozen product rises above its Tg some of the moisture present can evaporate and sublime through the product to the surrounding atmosphere, in this case the inside of the bag in which it is packed. Once there the water vapour freezes into ice crystals and becomes visible as `snow' on the product (see Fig. 17). With the reduction, for health reasons, in salt levels in bread products, this problem is likely to occur earlier in the products' frozen life. This is because salt is a material which has the ability to `hold on to' the moisture in the product thus preventing its èscape' as vapour.

Fig. 17

Ice crystals formed in bread pack.

If the problem occurs frequently it would be wise to check that your freezer is operating correctly (temperature at or below ÿ20ëC) and try to minimise any opening and closing of its door and check its defrosting cycle. It is also beneficial to remove product in strict rotation so that any one product does not spend too long in the freezer. In addition, care should be taken that any product which is removed from the freezer is not left in a warm atmosphere, as the localised melting of the ice particles provides a good environment for eventual mould growth.

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4.6 We are seeking to improve the quality of our bread products and are getting conflicting advice on what the optimum dough temperature ex-mixer should be. Can you advise us as to whether we should increase or decrease our dough temperature? The control of the temperature of the dough delivered at the end of mixing is a critical factor in ensuring consistent final product quality because of its contribution to gas retention in the dough, gas production by bakers' yeast and dough rheology for processing. Whatever your choice of final dough temperature it is very important to ensure that you are consistent from dough to dough. Choosing the appropriate dough temperature to aim for after mixing is independent of producing a dough with a consistent final temperature. In general, raising the final dough temperature will encourage the yeast to work faster and this will speed up fermentation. One of the disadvantages of this will be that the bulk dough density will change more rapidly with time; as the bulk dough density decreases, this can lead to greater problems with divider weight control while processing the batch. Since the yeast will be more active, you may find that you can slightly reduce the level that you are using provided you do not compromise final proof time and oven spring. If you are using an improver then by raising the dough temperature you will gain increased activity from the ascorbic acid present, which should improve dough gas retention. There will also be an increase in the contribution of the enzymic activity in the dough and you need to make sure this does not adversely affect dough processing. In general, raising the dough temperature will make the dough easier to mould into shape but in some circumstances you may find that the dough becomes stickier and you may need to reduce added water levels. Warmer doughs not only tend to ferment faster, they also tend to prove more uniformly and this can lead to a more uniform, and sometimes shorter bake. The key advantage in reducing the dough temperature is that you can better control gas production in the early stages of dough processing and limit the potential impact of dough stickiness. However, lower dough temperatures have an adverse impact on gas retention and so there can be a loss of product volume and crumb softness. If you have a fixed proof time then you will need to add more yeast with colder doughs in order to maintain proof volume for the same time. This can lead to problems of product uniformity in the oven arising from the increased temperature differential between the surface of the dough piece and its centre. A common problem arising from using cool doughs and high yeast levels can be the development of ragged crust breaks (BPS, pp. 84±5). The ex-mixer dough temperatures commonly used in baking range from 24± 32ëC with bulk fermentation processes using the lower end of the range and notime dough making processes the higher end. Reference


CAUVAIN, S.P.


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4.7 How can I calculate the amount of ice I need to replace some of the added water when my final dough temperature is too warm? Using an ice slush (a mixture of water and crushed ice) or crushed ice to keep control of the dough temperature at the end of mixing is a practical solution to unacceptably high dough temperatures in the summer months, in countries with hot climates, and with stronger flours, which may require long mixing times or high mixing energies. The cooling capacity of ice is at least four times that of cold water as heat energy is used up in converting the ice to water at 0ëC. The ice must be in a form which is easily dispersed and can quickly use up the heat in the dough. In order to calculate the quantity of ice needed to replace added water a `heat balance' scenario must be used. The heat to be removed from the added water (in order to cool it to the required temperature), must be balanced against the heat required to convert the ice to water and then heat that melted ice to the required water temperature. The following formulae can be used to determine the quantity of ice which must replace a portion of the recipe added water to obtain the required water temperature to control the final dough temperature. A `heat balance' is achieved as shown on Fig. 18. The formulae using metric standards are given. Wi weight of ice Ww required weight of recipe added water Tt temperature of tap water in ëC Tr required water temperature in ëC Heat, Q1, to be removed from added water Ww ÿ Wi Tt ÿ Tr 4:186 Specific heat capacity of water 4.186J/kg/ëC Heat, Q2 needed to melt ice and heat resulting water to the required water temperature Wi 334:6 Wi Tr 4:186 Latent heat of ice 334.6 For heat balance Q1 Q2

Eqn (1)

Ww ÿ Wi Tt ÿ Tr 4:186 Wi 334:6 Wi Tr 4:186 For example: 40 kg of water is required for a dough mix. Temperature of tap water is 20ëC. Required temperature of water for the dough is 10ëC. Calculate how much of the added water would need to be ice. To cool (40 kg ± wt of ice) of water from 20 to 10 requires Q1 heat to be removed.

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Fig. 18 Heat balance calculation.

Q1 40 ÿ Wi 20 ÿ 10 4:186 40 ÿ Wi 41:86 This is the heat àvailable' to melt Wi kg ice, and to heat that ice water to 10ëC Q2 Wi 334:6 Wi 10 ÿ 0 4:186 Wi 334:6 41:86 Using heat balance (Eqn 1), 40 ÿ Wi 41:86 Wi 334:6 41:86 41:86 40 ÿ 41:86Wi 376:46Wi 418:32Wi 1674:4 Wi 4 Of the 40 kg of water required for the recipe, 4 kg should be added as ice and 36 kg added as tap water at 20ëC. It is worth remembering that the water that is `locked-up' as ice at the start of the mixing is not available to dissolve ingredients or start the hydration processes of the damaged starch and proteins in the flour. The likely impact on dough development will be small but may be more significant if a very large


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mass of ice is used. In practical terms it is better to use crushed ice as this aids the rapid dispersion of the small ice particles through the dough. In theory cube ice may be used but this should be avoided as much as possible. If you are going to routinely add ice to your doughs, make sure that you have a large enough ice-making capacity. You will not only need to calculate the mass of ice that you are likely to need for your mixings but also need to take into account the ability of your ice-making machine to deliver ice at the required rate. You may need to have some form of buffer container to hold the ice ready for use in the bakery.

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4.8 We are considering the purchase of a new mixer for the manufacture of our bread using a no-time dough process. There are two types of mixer that seem to be appropriate for our plant production needs, the spiral-type and the CBPcompatible type, but before making our decision we need to understand any issues with respect to dough processing and final bread quality. Can you please advise us? The first point to make is that both mixer types are perfectly suitable for making bread using a no-time dough process. In many ways your choice will be dictated by the type of bread that you wish to make and the final characteristics that your products should have. We have listed below the main technical issues that you should consider in making your choice. Plant capacity and mixing times Clearly it is important to ensure that you can provide sufficient dough to run efficiently with minimal gaps between batches when the products reach the oven. It is usually a relatively simple calculation to determine the batch size capability of the mixer. You will also need to consider the mix cycle time; the length of time from the start of ingredient delivery to the mixer and delivery of the mixed dough to the divider. The mix cycle time will include the actual dough mixing time along with all of the loading and transfer times required. In general, for reasons discussed below, the actual mixing time (not the mix cycle time) for spiral-type mixers is longer than that for CBP-compatible mixers; typical mixing times would be 8±14 minutes for the spiral (see BPS, p. 96) and 3±5 minutes for the CBP. These times may vary but it is worth noting that optimum mixing times for CBP doughs are quoted as 2±5 minutes (Cauvain and Young, 2006). Energy input and dough development During the mixing cycle energy is transferred to the dough by the mechanical action of the impeller. This energy is an important part of the development of a gluten structure in the dough with the appropriate rheological and gas retention properties; in general the greater the energy input, the greater the dough development and the greater the gas retention properties of the dough (see BPS, pp. 92±3) though the precise effects of increasing the level of energy input to the dough will vary according to flour quality (Cauvain, 2007). The total level of energy transferred to the dough during mixing depends to a significant degree on the length of the mixing time; the longer the mixing time, the greater the total energy transferred. However, it has been known for some time (Cauvain, 2007) that the `rate' at which energy is transferred to the dough also has an impact; in general, the faster the mixing speed, the faster the rate of energy transfer and the greater the improvement in dough gas retention for a given set of ingredients and dough recipe. CBP-compatible mixers exploit this effect by running at a higher speed than many spiral-type mixers, which explains, in part, why optimum mixing times are shorter with CBP-type mixers.


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The rate of energy transfer to the dough during mixing also depends on the physical geometry of the mixing bowl and the impeller blades that are used. In the case of spiral-type mixers, the introduction of a static bar or a twin spiral arrangement may be used to increase the rate of energy transfer to the dough and shorten mixing times. In the case of the latter form of spiral mixer, you could argue that this is the equivalent of a CBP-type mixer but there are other considerations to be taken into account (see below). Dough temperature control There is a direct relationship between the input of energy to the dough during mixing and its final temperature; the higher the total energy input, the higher the final dough temperature for a given recipe and batch size. In dough mixing the most common way to control the final dough temperature is through the adjustment of the initial water temperature (Cauvain and Young, 2008). It is common practice to have a sufficient supply of chilled water available in the bakery for dough mixing to help with the control of the final dough temperature and in some cases ice or ice-slush may be added at the start of mixing (see 4.7). Typical final temperatures for CBP-type dough will be in the order of 28± 32ëC while those for spiral mixed dough would be 24±28ëC. Traditionally spiralmixed dough tends to have a lower final temperature because usually less energy is transferred during mixing. CBP-type dough tends to have a higher final dough temperature not only because of the higher energy input but because the increased dough development yields a dough with dough rheological characteristics that allow it to be readily processed on the dough make-up plant at the higher temperature. Dough gas bubble structure and product cell structure The creation of the gas bubble structure in dough depends on the entrainment and sub-division of air during dough mixing (Cauvain, 2007). Many factors influence the gas bubble population (i.e., the numbers and sizes of gas bubbles) in the mixed dough. The initial gas bubble structure in the mixed dough is a major contributing factor to the final product cell structure. It is significantly affected by the mixer type. This is an important issue, since with no-time doughs there is no significant opportunity during processing to modify the gas bubble population to reduce its average size. In practice, when the dough leaves the mixer, the main change for the gas bubble is to increase in size. Thus if a fine and uniform cell structure is required in the final product, essentially it must be created in the mixer (see also below). Because gas bubbles grow after leaving the mixer, it is easier to create a coarser cell structure in the final product. The measurement of gas bubble populations in mixed dough has shown that spiral-mixed dough has a higher average bubble size and a wider range of sizes than typically seen with CBP-type mixers (Cauvain et al., 1999). Since the initial gas bubble population is a major determinant of final product cell structure, this means that spiral-mixed dough tends to yield final products with a greater average cell size with a wider range of sizes; in practical terms the cell

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structure of bread from spiral-mixed dough will have a coarser and less even structure than those from CBP-type mixers (but see the following section). The modification of product cell structure The preceding comments on the creation of gas bubble populations and product cell structures are important in understanding one of the key principles of the CBP, namely the control of product cell structure through the modification of the mixer headspace pressure (Marsh and Cauvain, 2007). Spiral-type mixers do not commonly have a facility for controlling the mixer headspace pressure, as the mixer bowl is mostly open to the atmosphere. The bowl of the true CBP-compatible mixer can be isolated from the surrounding atmosphere by means of lowering a close-fitting lid. Historically, (Cauvain and Young, 2006) the atmospheric pressure in the mixing bowl was reduced below that of atmospheric pressure in order to create a finer and more uniform cell structure in the bread (with accompanying advantages for crumb softness). Later developments of the CBP-compatible mixer (Cauvain, 1994) include the facility to have pressures above or below atmospheric and, most importantly, to change from one pressure to another during the mixing cycle. This development enables the creation of different gas bubble populations in the dough and therefore different cell structures in the final product. In practice this means that the same mixer can be used to create the fine and uniform cell structure required for sandwich bread or the coarse open structure required for French bread types simply through the manipulation of mixer headspace pressure. References

(1994) New mixer for variety bread production. European Food and Drink Review, Autumn, 51±53. CAUVAIN, S.P. (2007) Breadmaking processes. In (eds S.P. Cauvain. and L.S. Young) Technology of Breadmaking, 2nd edn, Springer Science+Business Media, LLC, New York, USA, pp. 21±50. CAUVAIN, S.P. and YOUNG, L.S. (2001) Baking Problems Solved, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2006) The Chorleywood Bread Process, Woodhead Publishing Ltd, Cambridge, UK. CAUVAIN, S.P. and YOUNG, L.S. (2008) Bakery Food Manufacture & Quality: Water Control and Effects 2nd edn, Wiley-Blackwell, Oxford, UK. CAUVAIN, S.P., WHITWORTH, M.B. and ALAVA, J.M. (1999) The evolution of bubble structure in bread doughs and its effect on bread structure. In (eds G.M. Campbell, C. Webb, S.S. Pandiella and K. Niranjan) Bubbles in Food, American Association of Cereal Chemists, St. Paul, MN, pp. 85±88. MARSH, D. and CAUVAIN, S.P. (2007) Mixing and dough processing. In (eds S.P. Cauvain. and L.S. Young) Technology of Breadmaking, 2nd edn, Springer Science+Business Media, LLC, New York, USA, pp. 93±140. CAUVAIN, S.P.


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4.9 We are looking to buy a new final moulder for our bread bakery. Can you advise us on the key features we should look for and how they might impact on final bread quality? The main function of the final moulder is to change the shape of the individual dough pieces to fit the product concept and deliver them in the appropriate form for final proof. Since there are many different sizes and shapes of bread products, there is no single moulder able to meet the requirements of all them. A typical bread dough moulder will comprise a chute feeding the pieces into a series of rollers (2±4 in number). Typically the pieces entering the rollers will have a round shape and the sheeting process by the rolls will yield a flattened elliptical shape. Immediately on leaving the rollers the leading edge of the dough `pancake' is lifted by a chain and the dough piece is rolled up like a Swiss roll before being carried underneath a moulding or pressure board. The gap between the board and the moving belt of the moulder is adjusted to yield the desired shape. Side guide bars may be fitted under the moulding board to help deliver a cylindrical shaped dough piece (a most common shape for bread products). The behaviour of the dough piece depends in part on the dough-making process that has been used. Dough that has undergone a period of bulk fermentation has a low density with large pockets of gas trapped in the gluten structure. Dough pieces passing through the sheeting rolls will become degassed and this action can contribute to making the cell structure of the final product finer and more uniform. In some dough types, e.g. baguette and ciabatta, the large gas pockets are an integral feature of the final product and so de-gassing of the dough is not advisable. Instead the moulding action will be designed to aid the retention of the large gas bubbles, though mechanical moulding is never likely to deliver the same final product cell structure that can be achieved with hand moulding. Modern no-time doughs have relatively low levels of gas in them and so the de-gassing function of the sheeting rollers has limited value. Such doughs also have a different rheological character and respond quite differently to heavy pressures during final moulding. In many cases the pressures can lead to damage of the gas bubble structure in the dough, which in turn leads to quality problems in the final product (BPS, pp. 87±8). Such quality losses are less likely to occur with longer moulding boards. As a general rule fine cell structure in bread is obtained by sheeting thinly and using just enough pressure under the moulding board to achieve the required shape. This sheeting is best achieved gradually in moulders with a greater numbers of rolls. Reference


CAUVAIN, S.P.

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4.10 We are having problems keeping a uniform shape with our bloomers. They tend to assume a bent or `banana' shape (Fig. 19). This happens even though we take great care to straighten them when they are placed on the trays. Can you explain why we get this problem? This can be a common problem in the production of free-standing breads and can easily be explained, though in some cases the solution can be quite difficult to achieve. The banana shape is actually created towards the end of the final moulding stage. As the dough piece passes under the moulding board on the final moulder and is extended in shape by the rolling action, the ends of the piece reach the side guide bars. The effect of the guide bars is to slow down the progress of the two ends of the dough piece while the centre continues to move at a higher speed. If you look closely at the dough pieces as they travel under the pressure board, you will see this happening and observe that the dough piece already has the banana shape you refer to (see Fig. 20).

Fig. 19

Bloomer with bent shape.

During the passage of the dough under the moulding board the ends and the centre of the dough piece are subjected to different levels of `twisting' force. This means that even though you are straightening the dough pieces by hand and even though you are giving them 45 minutes proof there is sufficient elasticity left in the piece for it return to the shape that it had taken on during moulding. This problem is more severe in bloomers because the dough often has a stiffer consistency to help with retaining the traditional round cross-section after baking. The moulder should be set to reduce the variation in twisting forces between the different parts of the dough piece. You should try to reduce the pressure exerted by the moulding board by setting it up so that the dough piece only reaches its full length half way under the board; ideally about two-thirds of the way down the length of the board. If you cannot do this without compromising other aspects of shape (e.g., sealed ends), then the ideal solution would be to use a moulder with a longer moulding board. You may find similar problems with any free-standing cylindrical-shaped products. If you are taking a larger dough piece and cutting it into smaller


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Fig. 20 Schematic of bloomer dough piece passing under the moulding board.

individual pieces, you are likely to find that uneven moulding contributes significantly to variations in dough piece dimension after baking. You can gain some benefit by proving the dough at a lower temperature for a longer time. The longer time and the reduced temperature differential in the dough piece both help to yield a more `relaxed' dough piece entering the oven, which should expand in a more uniform manner. If you do reduce the proving temperature, remember to slightly reduce the humidity as well otherwise the dough pieces will begin to flow and lose their shape. If you cannot make adjustments to the moulder or proving conditions, you might try a slight increase in added water level but there is a delicate balance here because more water in the dough can cause the bloomer to assume a flatter appearance (Cauvain and Young, 2008). You may also find it helps to mix the dough longer since you are using a spiral mixer, making sure that you keep the final dough temperature the same as for normal production. Reference

and YOUNG, L.S. (2008) Bakery Food Manufacture and Quality: Water Control & Effects 2nd edn, Wiley-Blackwell, Oxford, UK.

CAUVAIN, S.P.

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4.11 Why is a bread dough piece coiled after sheeting? Does the number of coils achieved have any impact on bread quality? The rationale for coiling a dough piece is closely connected with the process of sheeting dough and the traditional use of a period of bulk fermentation after mixing to `develop' the dough ready for dividing and processing as unit shapes. The density of dough at the end of its bulk fermentation period is very low and as much as 70% of the dough volume may comprise gas bubbles, a mixture of mostly nitrogen and carbon dioxide of various sizes (Cauvain, 2003). Some of the gas bubbles may be very large in size (several cm) and if they are retained in the dough piece which enters the prover, these bubbles commonly lead to the formation of unwanted holes in the crumb of pan breads (although they may be acceptable in baguette and ciabatta). Such large gas bubbles can readily be expelled from the dough piece by flattening them by hand or by pinning. An alternative was to pass the dough backwards and forwards through the sheeting rolls of a pastry brake. A similar process to the latter was achieved by passing the dough through a series of pairs of rolls, one set mounted above another, and this is the basis of the most common form of bread dough moulders. The expression of the large gas bubbles from the dough piece is an important contributor to the formation of a fine and uniform cell structure in the baked product, which in turn, is an important contributor to bread crumb softness and brightness; both are seen as desirable characteristics in white and many other bread types. The formation of a round dough piece after dividing is a common practice, even if hand moulding is undertaken. When such dough pieces are passed through sheeting rolls, they form an elliptical shape, which is then coiled (rolled like a Swiss roll) to form a crude cylindrical shape for final processing (Marsh and Cauvain, 2007). The number of coils that are achieved when creating the cylinder depends mainly on the length of the ellipse and is determined to a large extent by the design of the sheeting head of the moulder and the speed at which the dough piece passes through it. The general view is that sheeting thinly, and the subsequent increase in the numbers of coils that are achieved, delivers a finer and more uniform crumb cell structure. However, it should be noted that the volume of gas in no-time dough pieces reaching the final moulder is considerably lower (typically

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Processed Meats: Improving Safety, Nutrition and Quality (Woodhead Publishing Series in Food Science, Technology and Nutrition)

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Dairy-Derived Ingredients: Food and Nutraceutical Uses (Woodhead Publishing in Food Science, Technology and Nutrition)

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Food Colloids: Proteins, Lipids and Polysaccharides (Woodhead Publishing Series in Food Science, Technology and Nutrition)

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