Science and Technology of Enrobed and Filled Chocolate, Confectionery and Bakery Products

Science and technology of enrobed and filled chocolate, confectionery and bakery products

Edited by Geoff Talbot

CRC Press Boca Raton Boston New York Washington, DC

Oxford

Cambridge

New Delhi

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 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 © 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 ISBN 978-1-84569-390-9 (book) Woodhead Publishing ISBN 978-1-84569-643-6 (e-book) CRC Press ISBN 978-1-4398-0136-9 CRC Press order number: N10028 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 Ann Buchan (Typesetters), Middlesex, UK Printed by TJ International Limited, Padstow, Cornwall, UK

Contents

Contributor contact details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. Talbot, The Fat Consultant, UK 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Enrobed and filled products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Scope of the book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part I 2

3

1 1 3 6 7 7

Formulation

Chocolate manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. Beckett, formerly of Nestlé Product Technology Centre, UK 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Raw materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Basic recipes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Grinding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Conching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 Sources of further information and advice . . . . . . . . . . . . . . . . . . 2.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Formulation of chocolate for industrial applications . . . . . . . . . . . . . P. Yates, Barry Callebaut (UK) Ltd, UK 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Ingredients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11 11 12 16 16 21 26 27 27 28 29 29 30 34

vi

Contents 3.4 3.5 3.6 3.7 3.8 3.9

4

5

6

7

Formulations for industry sectors . . . . . . . . . . . . . . . . . . . . . . . . . Speciality products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Health aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sources of further information and advice . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

40 45 49 51 52 52

Fats for confectionery coatings and fillings . . . . . . . . . . . . . . . . . . . . . G. Talbot, The Fat Consultant, UK 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Crystal structure and polymorphism of fats . . . . . . . . . . . . . . . . . 4.3 Range of coating and filling fats . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Effects of fat on quality and processing . . . . . . . . . . . . . . . . . . . . 4.5 Selecting the correct fat for application type . . . . . . . . . . . . . . . . 4.6 Trans fats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 Sources of further information and advice . . . . . . . . . . . . . . . . . . 4.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53

Compound coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. Talbot, The Fat Consultant, UK 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Cocoa butter alternatives in compound coatings . . . . . . . . . . . . . 5.3 Recipes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Flavourings and colourings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Effects of formulation on sensory and functional properties . . . . 5.6 Effect of fat choice on manufacturing process . . . . . . . . . . . . . . . 5.7 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 Sources of further information and advice . . . . . . . . . . . . . . . . . . 5.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fat-based centres and fillings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J. Birkett, AarhusKarlshamn Denmark A/S, Denmark 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Effects of ingredients on quality . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Recipes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Manufacturing processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 Stability and shelf-life issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 Sources of further information and advice . . . . . . . . . . . . . . . . . 6.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53 57 61 69 71 73 76 78 78 80 80 82 87 89 90 93 98 99 99 101 101 102 112 116 119 121 121 121

Caramels, fondants and jellies as centres and fillings . . . . . . . . . . . . 123 W. P. (Bill) Edwards, Bardfield Consultants, UK 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 7.2 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Contents

vii

Ingredients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gelled products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

127 138 142 147 149 150 151

Biscuits and bakery products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. Brown, Burtons Foods Ltd, UK 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Chocolate formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Emulsifiers in chocolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 Moisture barriers for caramel- and jam-containing biscuits . . . . 8.5 Non-hydrogenated coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6 Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.7 Quality issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 Fillings for bakery products . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.9 Future trends in chocolate enrobing . . . . . . . . . . . . . . . . . . . . . . 8.10 Sources of further information and advice . . . . . . . . . . . . . . . . .

152

7.3 7.4 7.5 7.6 7.7 7.8 7.9 8

9

Chocolate and couvertures: applications in ice cream . . . . . . . . . . . D. J. Cebula and A. Hoddle, Unilever R&D, UK 9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Features of ice cream and chocolate . . . . . . . . . . . . . . . . . . . . . . 9.3 Application processes, formats, requirements, defects . . . . . . . . 9.4 Inclusions in ice cream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Sources of further information and advice . . . . . . . . . . . . . . . . . 9.7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part II

152 153 155 155 156 157 159 161 162 162 163 163 164 171 178 180 181 182

Product design

10 Product design and shelf-life issues: oil migration and fat bloom . . G. Ziegler, Penn State University, USA 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 Mechanisms of oil migration and fat bloom . . . . . . . . . . . . . . . . 10.3 Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4 Optimizing product quality in relation to oil migration and fat bloom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6 Sources of further information . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

185 185 186 195 204 206 206 207

viii

Contents

11 Product design and shelf-life issues: moisture and ethanol migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. Talbot, The Fat Consultant, UK 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Mechanism of moisture migration . . . . . . . . . . . . . . . . . . . . . . . 11.3 Measurement of permeability . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 Reducing moisture migration . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.5 Alcohol (ethanol) migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7 Sources of further information and advice . . . . . . . . . . . . . . . . . 11.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Shelf-life prediction and testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P. J. Subramaniam, Leatherhead Food International, UK 12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Shelf-life testing methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3 Sensory changes during storage of chocolate confectionery . . . 12.4 Shelf-life prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.6 Sources of further information and advice . . . . . . . . . . . . . . . . . 12.7 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Controlling the rheology of chocolate and fillings . . . . . . . . . . . . . . . M. Wells, formerly of Cadbury Trebor Bassett, UK 13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2 Defining rheological terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3 How to measure the rheology of chocolate and fillings . . . . . . . 13.4 Typical chocolate flow curves . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5 Factors affecting chocolate rheology . . . . . . . . . . . . . . . . . . . . . 13.6 The rheology of fillings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.7 Issues with shell moulding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8 Issues with enrobing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.9 Issues with one-shot depositing . . . . . . . . . . . . . . . . . . . . . . . . . . 13.10 Dealing with viscoelasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.11 Sources of further information and advice . . . . . . . . . . . . . . . . . 13.12 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

211 211 212 214 216 229 231 231 231 233 233 234 243 249 251 252 253 253 255 255 256 259 263 265 273 278 280 281 282 282 283

14 Using microscopy to understand the properties of confectionery products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 K. Groves, Leatherhead Food International, UK 14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 14.2 Microscopy techniques and their uses . . . . . . . . . . . . . . . . . . . . . 286 14.3 Relationships between the microstructure of chocolate and

14.4 14.5 14.6 Part III

Contents

ix

coatings and their properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

298 307 307 307

Processing, packaging and storage

15 Ingredient preparation: the science of tempering . . . . . . . . . . . . . . . K. Smith, Unilever R&D, UK 15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.2 Effects of tempering on quality . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3 Polymorphism and phase behaviour of triacylglycerols . . . . . . . 15.4 Cocoa butter polymorphism . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.5 Changes during tempering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.6 Factors affecting tempering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.7 Measurement of temper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.9 Sources of further information and advice . . . . . . . . . . . . . . . . . 15.10 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Tempering process technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . K. Richter, Sollich KG, Germany 16.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2 Characteristics of cocoa butter . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3 Chocolate tempering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.4 Chocolate coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5 Chocolate moulding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.6 Aerated chocolate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.7 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Manufacturing processes: enrobing . . . . . . . . . . . . . . . . . . . . . . . . . . M. J. Bean, Baker Perkins Ltd, UK 17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 Types of enrobing machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3 Centre preparation and presentation to the enrober . . . . . . . . . . 17.4 Chocolate application case study . . . . . . . . . . . . . . . . . . . . . . . . 17.5 Chocolate handling systems within the enrober . . . . . . . . . . . . . 17.6 Environmental and hygiene issues . . . . . . . . . . . . . . . . . . . . . . . 17.7 Ancillary equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.8 Typical operating parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.9 Faults and remedies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.10 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.11 Sources of further information and advice . . . . . . . . . . . . . . . . .

313 313 314 315 322 324 330 333 337 338 339 344 344 344 346 355 359 359 361 361 362 362 363 376 377 379 385 388 390 390 394 396

x

Contents 17.12 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396

18 Manufacturing processes: chocolate panning and inclusions . . . . . G. Geschwindner and H. Drouven, Drouven & Fabry GmbH, Germany 18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2 Centres and raw materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3 Preparation of the centres: precoating . . . . . . . . . . . . . . . . . . . . . 18.4 Panning process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.5 Finishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.6 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.7 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.8 Sources of further information and advice . . . . . . . . . . . . . . . . .

397 397 398 400 403 405 406 412 412

19 Manufacturing processes: production of chocolate shells . . . . . . . . J. Meyer, Bühler Bindler GmbH, Germany 19.1 Fundamentals of chocolate shell production methods . . . . . . . . 19.2 Cold stamping technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3 Depositing, vibrating, cooling and demoulding . . . . . . . . . . . . . 19.4 Process conditions and product quality . . . . . . . . . . . . . . . . . . . . 19.5 Faults, causes and solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.7 Sources of further information and advice . . . . . . . . . . . . . . . . . 19.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

414

20 Manufacturing processes: deposition of fillings . . . . . . . . . . . . . . . . J. Meyer, Bühler Bindler GmbH, Germany 20.1 Modern processes for depositing fillings into premade shells: One-Shot technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.2 One-Shot process conditions and product quality . . . . . . . . . . . . 20.3 Faults, causes and solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.4 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5 Sources of further information and advice . . . . . . . . . . . . . . . . . 20.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

427

415 416 418 422 423 423 425 426

428 428 436 438 438 439

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441

Contributor contact details (* = main contact)

Chapters 1, 4, 5, 11 Geoff Talbot The Fat Consultant Suite 250 St Loyes House 20 St Loyes Street Bedford MK40 1ZL UK Email: [email protected]

Chapter 2 Dr S. T. Beckett Formerly of Nestlé Product Technology Centre Haxby Road York YO91 1XY UK Email: [email protected]

Chapter 3 Philip Yates UK Product Manager Barry Callebaut (UK) Ltd

Wildmere Road Banbury OX16 3UU UK Email: [email protected]

Chapter 6 J. Birkett AarhusKarlshamn Denmark A/S DK-8000 Aarhus C Denmark Email: [email protected]

Chapter 7 Dr Bill Edwards Bardfield Consultants 14 Durham Close Gt. Bardfield Braintree Essex CM7 4UA UK Email: BillEdwards@bardfield consultants.co.uk

xii

Contributor contact details

Chapter 8 M. Brown Technical Operations Manager Burtons Foods Ltd Pasture Road Moreton Merseyside CH46 8SE UK Email [email protected]; [email protected]

Chapter 9 D. J. Cebula* and A. Hoddle Unilever R&D Colworth Science Park Sharnbrook Bedford MK44 1LQ UK Email: [email protected]; [email protected]

Leatherhead Food International Randalls Road Leatherhead Surrey KT22 7RY UK Email: psubramaniam@leatherhead food.com

Chapter 13 Martin Wells 106 Golden Cross Lane Catshill Bromsgrove Worcs B61 0LA UK Email: [email protected] Formerly of Cadbury Trebor Bassett Bournville Birmingham UK

Chapter 14 Chapter 10 Professor G. R. Ziegler Department of Food Science Penn State University 341 Food Science Building State College PA 16801 USA

Kathy Groves Food Innovation Leatherhead Food International Randalls Road Leatherhead, Surrey KT22 7RY UK

Email: [email protected]

Email: [email protected]

Chapter 12

Chapter 15

Persis Subramaniam Food Innovation

K. W. Smith Unilever R&D

Contributor contact details Colworth Science Park Sharnbrook Beds MK44 1LQ UK

xiii

Peterborough PE4 7AP UK Email: [email protected]

Email: [email protected]

Chapter 18 Chapter 16 K. Richter Process-Engineering SOLLICH KG Siemensstraße 17–23 32105 Bad-Salzuflen Germany Email: [email protected]

G. Geschwindner and H. Drouven* Drouven & Fabry GmbH Hirzenrott 6 52076 Aachen Germany Email: [email protected]

Chapters 19, 20 Chapter 17 M. J. Bean Baker Perkins Ltd Manor Drive Paston Parkway

Joerg Meyer Technologist/Manager Pilot Plant Bühler Bindler GmbH Germany Email: [email protected]

1 Introduction Geoff Talbot, The Fat Consultant, UK

Abstract: Multi-component confectionery products with a chocolate coating are not new, the first ones having been developed during the early part of the 20th century. Their complexity has, however, increased tremendously during the past hundred years or so. One of the reasons for this has been the continual consumer demand for new taste and textural sensations. This means that, despite the well-established nature of this sector of the food industry and also despite the fact that many of the leading products were developed over 70 years ago, it is still a sector that is growing. This book is divided into three parts. Part I covers the main component parts of these multi-component products – chocolate, compound coatings, fat-based fillings, caramels, fondants, biscuits, bakery products and ice cream. Part II then goes on to discuss some of the product design issues related to enrobed and filled confectionery including fat and moisture migration, fat bloom, as well as the shelf-life, rheology and microstructure of chocolate. Part III deals with the processing and production of these products – tempering, enrobing, moulding, panning and cooling,. Key words: biscuits, caramels, chocolate, compound coatings, cooling, enrobed confectionery, enrobing, fat bloom, fats, filled confectionery, fillings, fondants, ice cream, market trends, microstructure, moisture migration, moulding, oil migration, panning, rheology, storage, tempering.

1.1

Introduction

The basis of all chocolate-enrobed and filled confectionery products is, of course, chocolate. To look at the way in which these products have developed means going back many centuries to central America where first the Mayans and then the Aztecs prized the cocoa bean for the drink that it produced. The Aztecs called this drink ‘chocolatl’ which means ‘warm liquid’. They called the cocoa bean, ‘the food of the gods’, a name which continues to this day in the Latin botanical name for the

2

Enrobed and filled chocolate, confectionery and bakery products

cocoa tree, Theobroma cacao. According to legends, Montezuma II, the emperor of the Aztecs, consumed 50 cups of chocolatl each day. Not only were cocoa beans used as the basis of this drink, they were also used as a form of currency amongst the Aztecs. The beans were first brought to Europe by Columbus and were one of the many things he brought back from his journeys to be presented to King Ferdinand and Queen Isabella of Spain. They were, however, largely ignored until the Spanish explorer Cortez arrived in Mexico in 1519. Thinking that he was a long-lost godking, the Aztecs greeted him and his crew with cups of chocolatl. This was the start of the downfall of the Aztec empire and the Spanish overpowered them. It took Cortez, though, to realise the potential of these beans and he introduced the drink to the Spanish aristocracy, after having added sugar to make it more to their taste. Its popularity spread across Europe and by the mid-17th century chocolate drinking houses had sprung up across England. It was not until 1828, when van Houten in The Netherlands found a way of pressing the fat from cocoa beans and then adding this back to a mixture of powdered bean and sugar that the first solid chocolate bars were produced. Further processing developments included the introduction in 1847 by Fry in Bristol of steam presses to separate out the fat more easily and thereby produce the first bars of plain chocolate. Milk chocolate came along some 30 years or so later having been developed by Daniel Peter in Vevey in Switzerland. Even in these early days, plain chocolate was used to coat centres such as fondants and nuts and the first ‘chocolate box’ is generally attributed to Cadbury. It is said (National Confectioners’ Association) that in 1868 Richard Cadbury decorated a box with a painting of his young daughter holding a kitten in her arms. Filled chocolates were mainly sold from trays (much like the luxury hand-made products of today). This was reflected in the names of two new Cadbury products launched in 1914 (Plain Tray) and in 1915 (Milk Tray, a chocolate box assortment still produced today). Other British chocolate box assortments that are still available, such as Terry’s All Gold and Rowntree’s (now Nestlé’s) Black Magic, were launched in the 1930s. Filled countlines (i.e products that were sold as an individual product, often in the form of a bar) were first produced in the United States in the early 20th century but some would say that the 1930s were the golden era of development for such products. Certainly many products still available today were first developed and launched in that decade in the United Kingdom (Opie, 1988):

• • • • • • •

1932 1935 1935 1935 1936 1937 1937

Mars Milky Way Aero Chocolate Crisp (renamed KitKat in 1937) Maltesers Rolo Smarties.

Many of these are now global brands.

Introduction

1.2

3

Enrobed and filled products

It is clear from this historical background that it didn’t take long after plain and then milk chocolate in a solid form were developed for manufacturers to start to make chocolate a part of a whole product and to use it to encase other components. This was partly to extend existing product lines by, for example, coating already commercially successful biscuit products with chocolate, partly to protect the centres from deterioration such as, for example, preventing the drying out and hardening of caramel by putting a coating of chocolate around it. The main impetus, though, was the ability to produce totally new products by combining cereal-based biscuits and wafers, fruits and nuts, aqueous-based systems such as caramels, jams and fondants and fat-based pralines in a chocolate wrapper. These developments gave new combinations of tastes and textures to satisfy consumers’ hunger for new sensations. In recent years cross-over and leveraging of brands from one product sector into another has been a major factor in developing new products. One of the most successful of these cross-over developments was the launch in 1989 of the Mars ice cream bar which was soon followed by many other ice cream products coated in ‘real’ chocolate (until then most ice cream bars had been coated in a chocolateflavoured compound coating). This has since been followed by the translation of other chocolate confectionery products into cake bars, biscuits, drinks, desserts and so on. It is useful, perhaps, at this stage to say exactly what is meant by ‘enrobing’ and ‘filling’. Enrobing means to apply a coating of, usually, chocolate (although it could also be a chocolate-flavoured coating or, indeed, a coating of any other flavour) to the outside of a product. Typical examples are coated biscuits, coated ice cream bars, coated cakes, coated fruits and nuts. The coating is usually applied by means of an enrober. This is a machine in which the products to be coated pass through a continuous ‘curtain’ of the coating. As they pass through, they are coated on the top, sides and bottom. Excess coating is removed and the remaining coating is crystallised by passing the coated product through a cooling tunnel. Some products are dipped into the coating and removed before again allowing the coating to crystallise and harden. Products that are typically dipped are ice creams on a stick (where the coldness of the ice cream begins to harden the coating even before passing into a blast freezer) and some hand-made confectionery products. Other products, particularly small items such as nuts and raisins are coated by panning. In this process the centres are continually moving in a rotating ‘pan’ (similar to a cement mixer) and the coating is sprayed on to them gradually building up in a number of layers. In other products, particularly where a thin coating is needed, the coating will be sprayed on to the surface of the centre. This is often used to apply thin barriers to reduce moisture and alcohol migration. On the other hand, there is ‘filled’ confectionery. Rather than start with the centre and put the coating around it, in filled confectionery we start with the coating and put the centre inside it. This is usually achieved by first making a shell of chocolate into which is deposited the filling. Since, in most applications, this

4

Enrobed and filled chocolate, confectionery and bakery products

leaves an incomplete coating on the product it is then finished by ‘backing off’ with further coating. For example, a praline centre can be deposited into a chocolate shell which, at that stage, consists of the top and sides of the eventual end product. Once the shell has been filled with the praline centre a further quantity of fluid chocolate is deposited on top of the praline centre to seal the whole product. This final ‘backing-off’ layer will be the base of the end product. Chocolate shells are usually produced in one of two ways. Either the moulds are filled with a surplus of chocolate and are then inverted and rotated both to coat the insides of the mould and allow excess chocolate to drain back for further use, or a small surplus of chocolate is deposited into the mould and a cold former is plunged into the chocolate to produce a shell with very accurately defined dimensions. In some instances, the centre is pressed down into the still liquid chocolate in the mould, allowing this to squeeze up the sides and over the top of the centre. This method is used where, for example, chocolate-coated biscuits are produced in a mould to allow the name of the product to be moulded into the top surface.

1.2.1 Definitions The fact that individual nations can be very protective about what constitutes ‘chocolate’ means that there is no single compositional standard or definition of chocolate across the world. For example, it took some 30 years or so for an EUwide definition of chocolate composition to be agreed, finally culminating in the Directive which came into force in August 2003. One of the main stumbling blocks (although, by no means, the only one) in global acceptance of a single compositional standard for chocolate has been whether or not non-cocoa vegetable fat can be added. For many years some EU countries permitted the use of vegetable fat up to a level of 5% in chocolate, while others did not. The 2003 EU Directive permits the use of up to 5% vegetable fat in chocolate but only under well-defined circumstances. The United States, on the other hand, does not permit the use of vegetable fat. In some ways, Codex Alimentarius could be seen as a global standard but even Codex has recently amended its standard to include now the use of vegetable fat. These different legislations will be discussed in more detail in Chapter 3, but it is perhaps instructive, even here, to compare the standards for milk chocolate in the EU, the USA and Codex (Table 1.1). If compositions move outside these definitions this does not mean that they are unsuitable for consumption and cannot be used. It simply means that they cannot be called ‘chocolate’ and need to be labelled in some other way. The most common form of labelling, in the United Kingdom at least, is to call them ‘chocolateflavoured coatings’. Other countries will have other forms of wording. Within the food industry, however, these ‘chocolate-flavoured coatings’ are often called compound coatings and, if non-cocoa butter fats are used they are referred to as compound coating fats (or, also, as cocoa butter alternatives). This book covers the use of both chocolate and compound coatings. Where it is unnecessary to distinguish one from the other, the term ‘chocolate’ will usually be used for simplicity. Where remarks apply solely to chocolate containing cocoa

Introduction

5

Table 1.1 Comparison of milk chocolate compositions in EU, USA and Codex (extracted from Yates, Tables 3.1, 3.2 and 3.3 of this book)

Total cocoa solids (dry) Non-fat cocoa solids (dry) Total milk solids (dry) Milk fat Total cocoa butter + milk fat Vegetable fat Cocoa butter

EU (%)

USA (%)

Codex (%)

25 min 2.5 min 14 min 3.5 min 25 min 5 max

10 min

25 min 2.5 min 12–14 min 2.5–3.5 min

12 min 3.39 min Not permitted

5 max 20 min

butter (for example, those coatings which require tempering to create a stable crystal form) this will be made clear in the text. Where remarks apply solely to compounds or compound coatings these will be referred to as such. While on the subject of components in chocolate, it should also be made clear that, unless otherwise stated, milk fat is taken to be the fat obtained specifically from cows’ milk. It may also be interchangeably referred to as anhydrous milk fat (AMF) or anhydrous butter. Butter itself is an emulsion of water droplets within a milk fat matrix, typically containing about 80% fat and 16% water. Although butter can be directly used in some enrobed centres (as an ingredient in caramels or biscuits, for example) it is more generally used in its anhydrous form. Many of the various phases of multi-component enrobed or filled products contain fat. Fat will be referred to in this volume in various ways. While the terms ‘oil’ and ‘fat’ will often be used interchangeably there will be occasions when ‘oil’ is used to denote the liquid form and ‘fat’ the solid form. Oils and fats are, chemically, tri-esters of three fatty acid groups on a backbone of glycerol. The food industry usually refers to these as ‘triglycerides’ or TG; the scientific and academic communities, however, call them ‘triacylglycerols’ or TAG. These terms will be used interchangeably in this book as will the corresponding terms for diglycerides/ diacylglycerols (DG/DAG) and monoglycerides/monoacylglycerols (MG/MAG). 1.2.2 Market trends Although chocolate has been around for a long time, EU production statistics still show a rising trend (Table 1.2), although consumption patterns are fairly static. According to CAOBISCO (Association of chocolate, biscuit and confectionery industries of the European Union) the greatest consumers of chocolate confectionery are the Swiss with, in 2006, a per capita consumption of 10.05 kg, closely followed by the United Kingdom with a per capita consumption of 9.97 kg. Indeed, in general, northern European countries are the greatest consumers of chocolate confectionery, occupying all of the top ten places in 2006. The United States ranks 12th in the CAOBISCO list with a consumption of 5.45 kg per head. Southern European countries have lower levels of consumption and this is related to the fact that it is more difficult to keep chocolate in a hard, solid, bloom-free condition in Mediterranean climates than it is in northern Europe.

6

Enrobed and filled chocolate, confectionery and bakery products

Table 1.2 EU production and consumption of chocolate confectionery (2004–6) (from CAOBISCO)

2004 2005 2006

Production (103 tonnes)

Consumption (103 tonnes)

2510 2766 2814

2381 2367 2382

Since many biscuits and wafers are chocolate coated it is useful just to mention the statistics for 2006 for these products (although these are not necessarily all chocolate coated). The Netherlands are by far the largest consumers of these products, at 18.72 kg per head, followed in second place by the United Kingdom with a consumption of less than half of that (9.22 kg per head).

1.3

Scope of the book

It is the intention of this book to be both one that can be read as a whole by taking the reader logically through the various aspects and processes of producing chocolate-enrobed and filled chocolate products, and also one that can be used as a reference text for specific aspects of the whole enrobing process. Logically, the production of chocolate is described beginning with a brief overview of the raw materials used and the mixing, refining and conching processes necessary to get chocolate in a form suitable for subsequent processing in tempering, enrobing and moulding equipment. The various formulations that can be used to produce chocolate, particularly chocolate for industrial use are also described. Legislation has already been referred to and a more detailed comparison of the legislation relating to chocolate composition in the main producing countries is made. Although chocolate is rich in both fat and sugar, it has a number of health benefits within its composition. Of these, perhaps the ones that make the headlines the most are the flavanols that are found in high cocoa-solids dark chocolate and which have been shown to help reduce the risk of cardiovascular disease as well as act as antioxidants. Even though the fat in chocolate is rich in saturates there is some evidence to suggest that some of the saturated fatty acids in cocoa butter may well be neutral in terms of blood cholesterol levels. As has already been mentioned, fats are present in many of the components of enrobed and filled confectionery and so an introduction is given to confectionery fat technology and to the use of fats in these products. To complement the chapters on chocolate production and composition there is also a chapter on compound coatings which describes the differences between the different types of compound fat and how they are used in place of chocolate. We then move on to look in more detail at the different types of centre that are either coated in chocolate or compound or which are used to fill shells of these materials. These chapters consider not only the more conventional ‘chocolate-box assortment’ types of centres based on fat-continuous fillings, caramels and fondants

Introduction

7

but also the more generic product sectors of biscuit and bakery products and ice cream. Part II of the book deals with various aspects of product design looking first at the major problems that can arise as a result of having multi-component systems. These are oil migration and fat bloom which are often inexorably linked together, and the analogous problems of moisture and alcohol migration. It is often necessary to take these into account when designing a new enrobed or filled product and the factors associated with both promoting and minimising them are described. There then follows three chapters relating to the chocolate itself which are also of importance in product design but more related to the process that the product will need to undergo or the storage of the product than to the actual product itself. These are the shelf life, rheology and the microstructure of the chocolate, coating or filling being used. Part III covers the all-important aspects of processing beginning with two chapters on tempering. The first looks at the science of tempering and, in particular, at what happens to the fat phase of chocolate during the different stages of tempering and temper measurement. The second considers the industrial methods available for tempering chocolate and how these are used in practice. Having tempered the chocolate (or not, in the case of compound coatings) it can then be used either to enrobe centres or to be formed into shells for subsequent filling. Both of these processes and the necessary equipment are described. In the case of a shell-moulded product it then, of course, has to be filled and so both the processes for filling pre-made chocolate shells and the process of forming both shell and filling in one operation (one-shot technology) are considered. After enrobing or production of a chocolate shell it is necessary to cool and crystallise the chocolate ready for packing. In this part of the book there is also a chapter on panning inclusions and small components such as nuts and fruits.

1.4

Acknowledgements

I would like to thank all the authors who have contributed chapters to this book. It is never easy fitting such things in with everything else that needs to be done, especially when facts need to be checked to ensure that in this fast-moving world they are still up to date, but they have all approached the task with professionalism and dedication. I would also like to thank the editors at Woodhead Publishing for their support and advice.

1.5

References

CAOBISCO.

Consumption Trends (2004–2006). http://www.caobisco.com/doc_uploads/ Charts/consumption_trends.pdf. CAOBISCO. Production Trends (2004–2006). http://www.caobisco.com/doc_uploads/Charts/ production_trends.pdf. NATIONAL CONFECTIONERS’ ASSOCIATION. ‘Facts and Trivia’. http://www.chocolateusa.org/ Story-of-Chocolate/how-america-loves-chocolate.asp OPIE R (1988). Sweet Memories, Pavilion Books Ltd, London.

Part I Formulation

2 Chocolate manufacture S. Beckett, formerly of Nestlé Product Technology Centre, UK

Abstract: This chapter describes the processes and ingredients involved in the large scale manufacture of liquid chocolate to give it the correct taste and flow properties. The quality criteria of the cocoa and its initial processing are particularly important. For the chocolate to be smooth tasting, the solid particles must be ground to less than 0.03 mm and this can be carried out in several different ways. The ground material is normally in the form of a powder or thick paste which is converted into a liquid in a machine called a conche. This machine is also able to modify the taste and remove unwanted acidic flavours from the chocolate. Key words: chocolate conche, cocoa beans, flow properties, grinding, liquefying.

2.1

Introduction

Most people think of chocolate as a solid material, which when eaten melts in the mouth, whereas to the confectioner it is a liquid that is poured into a mould or over the sweet centre. This chapter describes the processes and ingredients involved in the large scale manufacturing of this liquid chocolate. The final taste and texture depend strongly upon the ingredients being used. Their quality criteria and initial processing, where applicable, are the subject of the second section of this chapter, followed by some very basic recipes. More detailed recipes are given in a later chapter of this book. The particles of the non-fat ingredients themselves are relatively large, often greater than 1 mm in diameter. For the chocolate to be smooth this must be reduced to less than 0.03 mm. The way this is done is described and is very important for the final chocolate taste and texture. At this stage the chocolate is often in powder form and a machine, unique to the industry, called a conche is then used to turn it into a liquid. At the same time the taste is modified, in particular by the removal of

12

Enrobed and filled chocolate, confectionery and bakery products

acids contained in the cocoa beans. This chapter concludes by looking at quality characteristics followed by possible future developments in chocolate manufacture.

2.2

Raw materials

2.2.1

Cocoa based

Growing areas and conditions All commercial cocoa is grown within 20o of the equator. Although the cocoa trees originated in the north of southern and central America, the majority of the world’s cocoa is now grown in Africa, with 40% coming from the Ivory Coast alone. Significant amounts are now also produced in south east Asia. There are four types of cocoa or cacao tree (Theobroma cacao, L.) namely Criollo, Forastero, Trinitario and Nacional. These grow in areas of high rainfall that is evenly distributed throughout the year and prefer a high humidity, typically 70–80% during the day and up to 100% at night. The mean monthly temperatures should be between 18 °C and 32 °C with an absolute minimum of about 10 °C. About 90% of the world’s cocoa is grown by smallholders (Fowler, 2009), usually on farms with mixed cropping systems. The flavour of the bean depends not only upon the cocoa type, but also upon the soil and weather conditions and many other factors, especially the harvesting and fermentation. These different flavours can be experienced by tasting dark chocolates made from cocoa from single origins which are currently available as tablets. In many other products, beans from several sources are often blended in order to get a consistent flavour. Harvesting The flowers on the cacao tree develop from flower cushions on the trunk and branches. Some trees flower almost continuously, whereas others have welldefined periods of flowering (often twice a year). The flowers are pollinated by small insects such as midges. After five to six months, the fully developed pods are between 100 and 350 mm long and weigh between 200 g and 1 kg. When they ripen, most pods change colour – usually from green or red to yellow or orange. They are then cut by hand from the trunks and branches. The pods that are low on the trunk are cut with a machete (cutlass). The upper branches are harvested using a special knife fixed on a long pole. The crop does not all ripen at the same time so that harvesting has to be carried out over a period of several months. Pods are normally harvested every two to four weeks. In West Africa the main harvest period is from the beginning of October until December. The pods are opened to release the beans, either by cutting with a machete or cracking with a simple wooden club. There are about 30 to 45 beans in the pod covered in a sweet, white mucilaginous pulp and attached to a central core or placenta (Fig. 2.1). At this stage the beans do not contain the correct chemicals to

Chocolate manufacture

Fig. 2.1

13

Cocoa beans in pods (Fowler, 2009: 18) reproduced with the permission of Wiley-Blackwell.

give a chocolate flavour. The precursor flavours are mainly formed and developed during the subsequent fermentation and roasting processes. Fermentation In the fermentation stage the fresh beans are usually heaped in a pile or in a wooden box, typically for five days. In West Africa the beans are normally covered with banana leaves. The white pulp contains natural yeasts and bacteria which multiply causing the breakdown of the sugars and mucilage. This kills the bean and forms some of the flavour precursors. The whole fermentation process is critical for the final bean quality and is often monitored by purchasers using a cut-test (Fowler, 2009). This test involves cutting up to 300 beans into half lengthways to determine the proportion that are visibly mouldy, slaty, infested, germinated or flat (i.e. containing no nib or cotyledon). Slaty beans (more than 50% grey or slaty in colour) have not undergone fermentation, giving them a low level of cocoa flavour coupled with high levels of astringency. Fully fermented beans are brown, brown/ purple and purple in colour. Drying The fermented beans are then dried either in the sun or by artificial heating. It is very important that the moisture level is about 7–8%. At higher moisture levels the beans are very likely to become mouldy. This imparts an unpleasant flavour and so the beans cannot be used for chocolate making. If the beans are dried below about 6% they become very brittle and difficult to process. When drying beans with artificial heating, care must be taken to ensure that the

14

Enrobed and filled chocolate, confectionery and bakery products

smoke does not come into contact with the beans, otherwise it too will impart a flavour that will be present in the final chocolate and cannot be removed by subsequent processing. Roasting and winnowing The cocoa bean consists mainly of an outer shell surrounding two cotyledons. This shell is very hard and will damage processing machinery. It is also often encrusted with dirt and does not have a good cocoa taste and so must be removed. Traditionally the beans are roasted to produce more chocolate flavour and also to kill any microbiological contamination that may have arisen during the growing, fermentation, drying or transport. This loosens the shell from the cotyledon and once the beans have been broken in a cracker, the light shell can be removed in an air stream (winnowed) from the heavier centre, known as the cocoa nib. An alternative procedure is to heat the surface of the bean to release the shell, then break and winnow, before roasting the cotyledons. This process, known as nib roasting, is said to give a more even roast and to save energy, because the shell, which is being thrown away, is no longer being taken to a very high temperature. Roasting itself is normally at a temperature of between 110 oC and 140 oC and takes about 45 minutes to 1 hour. Grinding cocoa The nib contains approximately 55% of a fat known as cocoa butter. This is mainly solid at 20 oC, but is liquid at body temperature. The fat is contained in cells within the cotyledons and must be released by grinding to break up the cells and produce an ingredient called cocoa liquor or cocoa mass. It is normally best to grind it finer than 0.03 mm so that the cocoa liquor feels smooth in the mouth and most of the fat is released. Unlike chocolate, the finer the liquor is ground, the more easily it flows. The nib pieces are often bigger than 1 mm, so a large amount of size reduction is required and this is normally done in two or more stages. The first stage is often in an impact mill, where the cocoa nibs are broken by hammers or pins. The cocoa liquor produced is then made finer in a disc mill or one or more ball mills and is now ready for chocolate or cocoa butter production. The production of cocoa liquor is increasingly being carried out in the country of origin of the beans. Cocoa butter As was noted earlier, the cocoa liquor contains about 55% cocoa butter. The highest quality fat is obtained by pressing it out directly, leaving a hard cake material which is milled into cocoa powder for use in drinks and cakes and similar products. Cocoa butter can also be extracted chemically and/or treated to remove flavour and manufacture a deodorised fat.

2.2.2 Sugar Standard granulated sugar (sucrose) is normally used to make chocolate, although icing sugar or larger particle size sugar are sometimes preferred. Ideally the sugar

Chocolate manufacture

15

should have a narrow particle size distribution and have a low moisture content. Unlike in many other applications colour is not usually an important quality criteria. Low calorie, tooth-friendly and sucrose-free chocolates use sugar alcohols, often with other bulking agents such as polydextrose and artificial sweeteners, to replace the sucrose. These sometime require lower temperature conching and should be eaten in moderation because of their laxative nature.

2.2.3

Milk based

Full cream milk powder Chocolate contains a lot of small sugar particles and any moisture that is present will bind the particles together and stop the chocolate flowing properly. It is therefore important to remove all the water from the milk before it is used to make chocolate. The EU, Codex Alimentarius and some other legislation states that all the solid components of the milk, for example lactose and whey protein, must be in their natural proportions. This means that although lactose (milk sugar) is sometimes used in chocolate to reduce its sweetness (lactose is less sweet than sucrose) it is not part of the milk component for regulatory and labelling purposes. Milk can be dried in several ways, but the majority of the milk powder used in the chocolate industry has been spray dried. It is possible to dry the whole milk so that the powder includes the milk fat and this is said to have a better flavour than when skimmed milk is used. Roller dried full cream milk powder is considered better by some manufactures as the chocolate produced tends to have a lower viscosity. Skimmed milk powder and butter oil Many manufacturers prefer to use skimmed milk powder and then add in the milk fat (butter oil) during the processing. This tends to give the liquid chocolate better flow properties than when full cream milk powder is used. Chocolate crumb In the United Kingdom, United States and some other countries, chocolate crumb is used. This was developed in the early part of the 20th century, when milk powders had poor keeping qualities, and is an ingredient that can be stored and used over a period of more than a year. It is normally made by drying condensed milk and adding cocoa liquor during the later stages of this process. The sugar and the natural antioxidants in the cocoa liquor give the long shelf-life, but the Browning reaction, which takes place during the drying stage, gives it a cooked flavour. The actual crumb processes are often highly kept secrets, as they provide the means by which several manufacturers obtain their house flavours.

2.2.4 Emulsifiers Part of the enjoyment of eating chocolate is the way it melts and flows in the mouth.

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This is in part due to the way in which the cocoa butter coats the solid particles. To help it do so, an emulsifier (surface active agent) is often added to the chocolate at a low level, normally less than 0.5%. Traditionally this is lecithin produced from soya or sunflower and is claimed to have beneficial health effects at higher levels. Other emulsifiers are used, sometimes to produce special shaped sweets or to reduce the formation of the white mould-like spots on chocolate known as chocolate bloom (see later chapters).

2.3

Basic recipes

2.3.1 Dark chocolate Dark chocolate is made from cocoa liquor, sugar and cocoa butter. Many contain a small amount of milk fat to reduce the formation of chocolate bloom. High cocoa content chocolates do not contain any added cocoa butter (all the cocoa butter present comes from the cocoa liquor).

2.3.2 Milk chocolate Milk chocolate is the same as dark chocolate, but with milk solids and fat replacing some of the cocoa liquor. Legislation is very strict about how much cocoa liquor and milk must be present. In some countries a high level of milk content must be labelled as household milk chocolate or its equivalent. When using chocolate crumb, the milk, sugar and most, if not all the cocoa liquor are already together as a single ingredient, which only needs grinding, followed by the addition of cocoa butter and emulsifiers at the conching stage.

2.3.3 White chocolate White chocolate is made from milk powder, sugar and cocoa butter. Deodorised cocoa butter is usually preferred to avoid the off-flavours present in pressed cocoa butter.

2.4

Grinding

2.4.1 Importance of particle size Most of the solid ingredients are about 1 mm or more in diameter. The tongue will detect particles larger than 0.03 mm and the chocolate will appear to be gritty. The finer a milk chocolate is milled, the smoother and creamier it becomes. Dark chocolates on the other hand increase in cocoa flavour as they are made finer. Often, milling produces a lot of very fine particles of less than 0.005 mm in size. The surface of these particles needs to be coated with fat to make them flow, so that unless extra fat is added the chocolate has a high viscosity and tends to melt less

Chocolate manufacture

Fig. 2.2

17

A five-roll refiner.

easily, often remaining in the mouth with a slightly clay-like texture. Chocolate is therefore the opposite to cocoa, which normally gets much thinner when it is milled to be smaller. Good grinding therefore involves breaking the bigger particles without producing too many very small ones, in other words having a narrow particle size distribution. This is often best achieved by having a series of milling events each of about 4- or 5-fold reduction, rather than one very big breaking procedure.

2.4.2 Two- and five-roll refining Five-roll refiners (Fig. 2.2) have been used for very many years to grind chocolate and other industrial products such as paints and pigments. For many years the sugar or crumb was dry milled in a hammer mill and the powdered product added to some of the fat and remaining ingredients before being milled on the five-roll refiner. More recently it has become more common to mix all the ingredients (apart from some of the fat and emulsifiers) and pre-mill on a two-roll refiner to about 0.120 mm, before feeding the product directly into a series of five-roll refiners operating in parallel (Fig. 2.3). The initial mixing is critical because the refiners need a liquid/pasty texture to operate. Failure to do so may result in separation of the ingredients or in extreme cases the material being thrown off one of the rolls into the room. The two-roll refiner consists of two cylinders, placed horizontally side by side, which turn in opposite directions so as to pull the paste into the gap between them. The pressure and shear in the gap mainly breaks the bigger particles and also coats

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Fig. 2.3 Diagram of two- and five-roll refiner chocolate making plant (Beckett, 2008: 64) reproduced with the permission of the RSC.

some of the newly formed surfaces with fat. Shear is related to the difference in speed between the two moving surfaces divided by the distance between them. This means that if two surfaces are travelling at very different speeds and are very close together, there is a very high shearing action, which will pull the particles apart. This is the operating principle of both types of roll refiner. The paste produced by the two-roll refiner is fed along moving belts into the feed hoppers of several five-roll refiners (Fig. 2.3). As its name suggests, the five-roll refiner consists of five slightly barrel-shaped horizontal cylinders, with four of the cylinders placed one above the other. The first roll or feed cylinder is placed below the others, but on the side so that a feed ‘hopper’ is formed between it and the second cylinder (Fig. 2.4). The five-roll refiner has a much smaller throughput than the two-roll one, as it has four crushing gaps, compared with one, and also as the chocolate is finer at this stage, it has many more particles to break, especially when producing a fine chocolate with a maximum particle size of less than 0.02 mm. The cylinders are hollow and are temperature controlled by flowing water through them. They are also pressed so closely together that the pressure bends the barrel shape so that there is a uniform straight gap between the cylinders. A knife blade scrapes the back of the fifth cylinder removing the chocolate in the form of flakes or a powder. Each successive roller is faster than the previous one which makes the chocolate form a continuous film proceeding up the refiner rather than keeping going round and round the bottom one. The thickness of this film depends on the gap between that particular roller and the one below it. The actual final particle size depends upon the gaps between the rolls and their relative speeds. In modern roll refiners the speed of the individual rolls is fixed and the size is mainly controlled by adjusting the gap between the first two rolls, that is, the ‘hopper’. The texture of the feed is continually changing so this gap keeps requiring adjustment. Refiner manufacturers have automated this by measuring the thickness of the chocolate film just before the knife removes it and then using this to control the feed gap. The temperature of the rolls alters the texture/viscosity of the film of chocolate

Chocolate manufacture

19

2 1 4

1 3

Fig. 2.4 Diagram of a five-roll refiner. 1, chocolate film; 2, thickness monitor; 3, chocolate feed hopper; 4, chocolate flake from scraper.

by changing the flow properties of the fat present. Because the roller surfaces are turning at a high speed, there is a centrifugal force on the individual particles trying to throw the chocolate from the roll. The film however holds it on, as long as it remains intact. Good temperature control is therefore needed when grinding chocolate. As the rollers press against the particles, they not only cause breakage but they also rub some fat onto the newly broken surfaces. In addition, newly formed sugar surfaces are chemically very reactive and able to adsorb the volatile flavours given off by cocoa, which is being crushed close by. This means that chocolate made using roll refiners will taste different to one made with the same ingredients, but where these ingredients are milled individually.

2.4.3 Dry grinding In the roll refiner the different ingredients are all milled together. Sugar breaks very differently from milk powder, but it is necessary to mill so that the biggest particles are of the required size. This results in the sugar, which breaks very easily being over-milled relative to the milk, which is much more rubbery and harder to break. As a consequence there is a relatively large number of small particles, giving the liquid chocolate a higher viscosity. This can be overcome by grinding the ingredients separately. The cocoa liquor should already be fine enough so in essence this means having a sugar mill and a milk powder mill. Both can be milled by hammer mills, without any fat being present. Having two mills is industrially unsatisfactory. A single air classifier mill can process them together and still minimise the production of very fine particles. The sugar and dried milk particles are fed together onto a milling disc. The metal hammers, wedges or pins at the edge of the disc rotate at very high speed hitting the particles, breaking some and chipping pieces off others. At the same time air is blown through the milling chamber. This carries the particles with it as

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it passes through the classifier. This is usually a rotating hollow cylinder with slits cut into the side. The smaller particles can travel at almost the same speed as the air and so pass through the classifier. Larger ones, however, travel much slower because of their weight and size, and are hit by the rotating bars of the classifier and knocked back into the milling chamber for further breakage. The smaller ones continue moving with the air until they reach the cyclones and filter bags where they are collected for further processing in the conche. The larger particles will recirculate through the classifier and milling chamber as many times as is necessary for them to be broken into pieces small enough to pass through into the cyclone. This means that any small sugar particles which are chipped or smashed off the larger crystals pass straight out of the mill, but some of the sugar and most of the milk will recirculate through the mill several times. The size of the particles can be controlled in two ways. One is to adjust the speed of the classifier. The faster it rotates the more particles are recirculated and the finer the final product. Alternatively the air flow can be changed. Faster moving air will carry more particles with it and thereby increase the particle size. Chocolate crumb can also be milled in this type of machine, although fat contents above about 12% may require the circulating air to be cooled. This is because milling generates heat, melting the fat and making the product sticky. This may eventually block up the pipe-work, stopping production.

2.4.4 Batch systems The above processes are often carried out at several tonnes per hour by large scale chocolate manufacturers, who often supply other small and even large scale companies, who manufacture confectionery products. Some smaller scale manufacturers use batch processes to process perhaps a few tonnes per day. This type of machinery is particularly popular when making chocolate flavoured coatings, for example a recipe where the cocoa butter is partially or wholly replaced by some form of vegetable fat. Most include the liquefying/taste changing processes that take place in the conche during large scale chocolate manufacture. There are many types of device, perhaps the most common being based upon ball mills or on a drum with internal scraping/breaking elements commonly known as a Macintyre refiner conche, manufactured, amongst others, by Low and Duff (Developments) Ltd (LADCO) UK and Lloveras (Spain). Ball mills The mills contain a large number of balls which hit each other as they tumble in a rotating container or by central turning agitators. The balls impact and rotate, breaking any particles that are caught between them and then pushing the smashed particles away. Smaller particles can move away faster and are less likely to be broken. This type of machine therefore tends to produce a relatively narrow particle size distribution. Several passes through the ball mill are likely to be needed in order to reach the required fineness for chocolate. Usually as the chocolate gets finer, smaller balls are used, coupled with a higher agitation speed.

Chocolate manufacture

21

These mills tend to be more efficient at smaller particle sizes. This type of mill has three problems: 1) It requires a liquid feed material and so needs a relatively high fat pre-mix and some pre-milling. 2) It is not able to coat the newly broken surfaces properly with fat. For this reason it is common to pass the milled material through a high shearing in-line liquefier before returning it to the input of the same or another ball mill. 3) It is completely enclosed, which is good because the chocolate remains free from external contaminants, but means that unwanted acidic flavours are not removed. Some systems incorporate taste changers. These can take the form of pouring the liquid chocolate over a spinning disc and blowing air over it. Macintyre refiner conches This machine has a temperature controlled jacketed drum with a serrated inner surface (Fig. 2.5). Particles are broken by spring loaded scrapers that rotate inside it. Air blown through it provides a forced ventilation which removes moisture and some flavour volatiles. Between 50 kg and 5 tonnes can be processed in a period of 12 hours or more depending upon the final required particle size. Unlike the ball mill, this type of machine is more efficient with larger particle sizes, as with smaller ones the particles can move out of the way rather than be broken, especially in lower viscosity chocolates. In order to reduce processing time, therefore, it can be useful to do the initial breakage in this type of machine, but then produce the final fineness in a ball mill. An alternative combination feeds the Macintyre with material from a two-roll refiner. These refiner/conches can operate with powdery/pasty feed material.

2.5

Conching

2.5.1 Flavour changes The cocoa fermentation and roasting processes produce the precursors and some final components of the chocolate flavour, which are modified in the conche. In addition certain acids are present in the cocoa, which give an unpleasant ‘vinegar’ flavour that needs to be removed from most chocolates. Recent studies (Ziegleder, 2004) have shown that conching also redistributes the flavour chemicals within the chocolate. As the ingredients enter the conche, about half of these flavours are associated with the cocoa and most of the rest are within the fat phase. Less than 5% are associated with the sugar. At the end of conching, an equilibrium is almost reached with about a third of the chemicals attached to each of these three components. It must also be remembered that it is possible to over conche and produce a very bland chocolate. There is still very much an art in combining the ingredients, recipe and processing to get the best tasting chocolate for a particular product.

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(a)

(b)

Fig. 2.5 Schematic diagram (a) and photograph (b) of Macintyre type refiner/conches.

The conche does this by stirring and mixing and allowing air to remove some of the volatiles. In addition the chocolate masse may be heated up to 100 oC or even higher, to cause the Maillard reaction and introduce cooked notes. However, at this stage, the moisture is low (