Novel Food Processing Effects on Rheological and Functional Properties
Electro-Technologies for Food Processing Series Series Editor
Hosahalli S. Ramaswamy
McGill University Department of Food Science Ste-Anne-de-Bellevue, Quebec, Canada
Novel Food Processing : Effects on Rheological and Functional Properties, edited by Jasim Ahmed, Hosahalli S. Ramaswamy, Stefan Kasapis, and Joyce I. Boye
Electro-Technologies for Food Processing Series
Novel Food Processing Effects on Rheological and Functional Properties
Edited by
Jasim Ahmed Hosahalli S. Ramaswamy Stefan Kasapis Joyce I. Boye
Boca Raton London New York
CRC Press is an imprint of the Taylor & Francis Group, an informa business
CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2010 by Taylor and Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number: 978-1-4200-7119-1 (Hardback) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http:// www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Novel food processing : effects on rheological and functional properties / edited by Jasim Ahmed … [et al.]. p. cm. -- (Electro-technologies for food processing series) Includes bibliographical references and index. ISBN 978-1-4200-7119-1 (alk. paper) 1. Food industry and trade--Quality control. 2. Food industry and trade--Technological innovations. 3. Food--Analysis. I. Ahmed, Jasim. TP372.5.N685 2010 664’.07--dc22 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com
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Contents Series Preface.....................................................................................................................................ix Preface...............................................................................................................................................xi Editors............................................................................................................................................. xiii Contributors...................................................................................................................................... xv Chapter 1.
Introduction and Plan of the Book................................................................................1 Jasim Ahmed, Hosahalli S. Ramaswamy, Stefan Kasapis, and Joyce I. Boye
Chapter 2.
Effect of Radio-Frequency Heating on Food................................................................7 Valérie Orsat
Chapter 3.
Ohmic Heating Effects on Rheological and Functional Properties of Foods .................................................................................................... 21 Michele Marcotte, Hosahalli S. Ramaswamy, Yousef Karimi-Zindashty, and Mohammad R. Zareifard
Chapter 4.
Effect of High Electric Field on Food Processing...................................................... 35 A. Muthukumaran, Valérie Orsat, T. R. Bajgai, and G. S. V. Raghavan
Chapter 5.
Pulsed Electric Fields: A Review on Design............................................................... 47 Sally Alkhafaji and Mohammed Farid
Chapter 6.
Effect of Ultrasound on Food Processing................................................................... 65 Jordi Salazar, Juan A. Chávez, Antoni Turó, and Miguel J. García-Hernández
Chapter 7.
Ultrasound Processing: Rheological and Functional Properties of Food................... 85 Kasiviswanathan Muthukumarappan, B. K. Tiwari, Colm P. O’Donnell, and P. J. Cullen
Chapter 8.
Effect of Irradiation on Food Texture and Rheology................................................ 103 Paramita Bhattacharjee and Rekha S. Singhal
Chapter 9.
Ozone and CO2 Processing: Rheological and Functional Properties of Food..................................................................................................... 127 Kasiviswanathan Muthukumarappan, B. K. Tiwari, Colm P. O’Donnell, and P. J. Cullen
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Contents
Chapter 10. Gelation and Thickening with Globular Proteins at Low Temperatures..................................................................................................... 147 Ruben Mercade-Prieto and Sundaram Gunasekaran Chapter 11. Fundamental Considerations in the Comparison between Thermal and Nonthermal Characterization of Bioglasses.............................................................. 187 Stefan Kasapis Chapter 12. Effect of High-Pressure and Ultrasonic Processing of Foods on Rheological Properties..............................................................................................207 Jirarat Tattiyakul and M. A. Rao Chapter 13. Effect of High Pressure on Structural and Rheological Properties of Cereals and Legume Proteins................................................................................................. 225 Jasim Ahmed Chapter 14. High-Pressure Treatment Effects on Food Proteins of Animal Origin.................... 257 Pedro A. Alvarez, Hosahalli S. Ramaswamy, and Ashraf A. Ismail Chapter 15. Functional Properties and Microstructure of High-Pressure-Processed Starches and Starch–Water Suspensions.................................................................................. 281 Yeting Liu, Weibiao Zhou, and David Young Chapter 16. Effect of High Pressure on Textural and Microstructural Properties of Fruits and Vegetables . ........................................................................................................ 301 Navin K. Rastogi Chapter 17. Pressure-Shift Freezing Effects on Texture and Microstructure of Foods............... 323 Songming Zhu and Hosahalli S. Ramaswamy Chapter 18. Issues and Methods in Consumer-Led Development of Foods Processed by Innovative Technologies............................................................................................ 337 Armand V. Cardello and Alan O. Wright Chapter 19. Novel Techniques for the Processing of Soybeans.................................................... 373 Joyce I. Boye and S. H. Rajamohamed Chapter 20. Supercritical Fluid Extrusion: A Novel Method for Producing Microcellular Structures in Starch-Based Matrices.........................................................................403 Sajid Alavi and Syed S. H. Rizvi
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Contents
Chapter 21. Rheological Properties of Liquid Foods Processed in a Continuous-Flow High-Pressure Throttling System................................................. 421 Rakesh K. Singh and Litha Sivanandan Chapter 22. Food Frying: Modifying the Functional Properties of Batters ................................ 437 Michael Ngadi and Jun Xue Chapter 23. Allergenicity of Food and Impact of Processing...................................................... 459 Andreas Lopata Index............................................................................................................................................... 479
Series Preface Novel Food Processing: Effects on Rheological and Functional Properties, edited by Jasim Ahmed, Hosahalli S. Ramaswamy, Stefan Kasapis, and Joyce I. Boye, is the first issue under the general umbrella of edited books in the Electro-Technologies for Food Processing Book Series involving the application of electro-technologies for various aspects of food processing, from pasteurization to sterilization, food preparation to food formulations, shelf-life extension to promoting food safety, food spoilage control to enhancing safety of foods, and from alternate to novel sources of the use of energy. Electromagnetic technologies offer unlimited potential to processing applications in foods. Industrially, electro-technologies provide unique opportunities and advantages not necessarily found in other techniques. The book series will look at each of them in detail, especially from the point of view of various industrial food processing applications. Each book in this series is expected to be devoted to a specific area of electro-technology, covering all aspects of its science and engineering, chemistry and physics, biochemistry and nutrition, quality and safety, and development and technology, both basic and applied. Notable among the novel approaches in heating and food processing techniques are microwave and radio-frequency heating, electrical resistance or ohmic heating, induction, and infrared heating applications. Use of pulsed electric fields, high-frequency magnetic fields, electric shockwaves, pulsed light, UV radiation, and ionizing irradiation offer potential nonthermal alternatives to food processing. On a different note, these also include such separation techniques as ultrasonics, electroacoustic dewatering techniques, electrodialysis, and ion-exchange systems. Stretching it further, one can look at other electromagnetic applications in spectroscopy, near infrared (NIR), Fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR) techniques finding their way into analytical and imaging concepts. This book is special in that, rather than focusing entirely on one technology, it is focused on the rheology and functionality associated with all novel methods. The leading editor, Jasim Ahmed, has done a wonderful job of bringing together contributions from global experts focusing uniquely on structure, microstructure, rheology, and functionality issues related to the various advanced technologies. This volume has been designed to be a valuable tool to graduate students and researchers as a source of scientific information and is a useful addition to any library devoted to life sciences. Hosahalli S. Ramaswamy Book Series Editor
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Preface Food processing is gradually moving in a new direction, incorporating technologies from other fields and at the same time taking into account consumers’ concerns about food safety, quality, and sensory attributes. The main reason for writing this book at the present time is to make available the wealth of knowledge becoming available on novel processing and its effects on food products. The concept was initiated by the leading editor (Jasim Ahmed), who intended to publish a book on the rheological characteristics of food proteins as affected by novel processing. After discussions with the second editor (Hosahalli S. Ramaswamy) and considering feedback from reviewers of the original book, it was proposed to the publisher to broaden the concept to rheology and functionality of foods. Meanwhile, the complementary expertise of the other two editors (Stefan Kasapis and Joyce I. Boye) and their meticulous input enabled the successful handling of the project. The chapters in this book are authored by international peers who have both academic and professional credentials. The book illustrates in a very clear and concise fashion the structure–property relationship. It is intended for scientists; technologists/engineers working in the area of food processing, process equipment design, and product development; and students of food science, technology, nutrition, health science, and engineering. The editors thank all of the contributors and, in many cases, their students and spouses for their dedicated efforts in the production of this book. We express our appreciation to our spouses and children for their understanding and encouragement during the preparation, editing of manuscripts, and constructive discussions. The leading editor (Jasim Ahmed) gratefully acknowledges the support of Dr. Sunil K. Varshney, Director of Polymer Source Inc., in the many tasks involved in editing a book in a highly demanding industrial environment. Special thanks are due to Steve Zollo of Taylor & Francis for his constant encouragement and excellent communication. Jasim Ahmed Hosahalli S. Ramaswamy Stefan Kasapis Joyce I. Boye
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Editors Dr. Jasim Ahmed has been associated with food processing teaching, research, and industry for the last 16 years in India, the Middle East, and Canada. He has both bachelor’s and master’s degrees in food and biochemical engineering and a PhD in food technology. He has published more than 80 peer-reviewed research papers, 15 industry-oriented technical papers, and 11 book chapters. He has served as special editor for three peer-reviewed international journals and is currently serving as one of the editors of the International Journal of Food Properties (Taylor & Francis). He has worked on food product development, food rheology, structure, nanocomposites, and the thermal behavior of food and biomaterials. He has extensively studied high-pressure-assisted textural modifications of protein foods and starches. Dr. Hosahalli Ramaswamy is a professor in the Department of Food Science at McGill University, Canada. He has developed a strong research program at McGill in the area of food process engineering. His research activities include overpressure thermal processing of foods in thin profile flexible and semi-rigid containers in still and rotary autoclaves, continuous aseptic processing of particulate low acid foods, food extrusion, food quality optimization, application of microwaves for food processing and drying, evaluation of thermophysical properties of foods, food system rheology, ultrahigh pressure processing, ohmic heating and the use of artificial intelligence for characterizing and modeling food processing and quality. He has to his credit more than 250 publications and several book chapters, and has edited 5 books. He has also authored a textbook on food processing. He is currently serving as editor for the Journal of Food Engineering. Dr. Stefan Kasapis is a professor at RMIT University, Australia. He has an established reputation in research on conformation, interactions, and functional properties of food hydrocolloids and co-solutes. His expertise extends from the gelation properties of high-water systems to the vitrification phenomena of high-solid mixtures. He is the author of more than 100 peer-reviewed publications in reputable food science journals and seven book chapters, and the inventor of eight international patents. He serves as editor of Food Hydrocolloids and is a member of the editorial board of Carbohydrate Polymers. He organized the 9th International Hydrocolloids Conference in June 2008. Dr. Joyce I. Boye is a research scientist with Agriculture and Agri-Food Canada. Her research in the past 15 years has been directed at developing techniques for the isolation, extraction, and characterization of proteins from both animal and plant sources. In the past ten years, Dr. Boye and her research team have done extensive work on oilseeds and pulses, working in collaboration with industries from the private sector to develop new processing techniques and products. She is the senior author of several confidential industrial reports and has a total of over 128 scientific publications/abstracts/technical presentations, including five book chapters.
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Contributors Jasim Ahmed Polymer Source Inc. Dorval Montréal, Québec, Canada
[email protected] or
[email protected] Sajid Alavi Department of Grain Science and Industry Kansas State University Manhattan, Kansas
[email protected] Sally Alkhafaji Department of Chemical and Materials Engineering The University of Auckland Auckland, New Zealand
[email protected] Pedro A. Alvarez Department of Food Science Macdonald Campus of McGill University Ste Anne de Bellevue, Québec, Canada
[email protected] Armand V. Cardello US Army Natick Soldier R, D&E Center Natick, Massachusetts
[email protected] Juan A. Chávez Sensor Systems Group Department of Electronic Engineering Universitat Politècnica de Catalunya Barcelona, Spain
[email protected] P. J. Cullen School of Food Science and Environmental Health Dublin Institute of Technology Dublin, Ireland
[email protected] Mohammed Farid Department of Chemical and Materials Engineering The University of Auckland Auckland, New Zealand
[email protected] T. R. Bajgai Department of Bioresource Engineering Macdonald Campus of McGill University Ste Anne de Bellevue, Québec, Canada
[email protected] Miguel J. García-Hernández Sensor Systems Group Department of Electronic Engineering Universitat Politècnica de Catalunya Barcelona, Spain
[email protected] Paramita Bhattacharjee Department of Food Engineering and Technology Institute of Chemical Technology Matunga, Mumbai, Maharashtra, India
[email protected] Sundaram Gunasekaran Department of Biological Systems Engineering University of Wisconsin-Madison Madison, Wisconsin
[email protected] Joyce I. Boye Food Research and Development Centre Agriculture and Agri-Food Canada St Hyacinthe, Québec, Canada
[email protected] Ashraf A. Ismail Department of Food Science Macdonald Campus of McGill University Ste Anne de Bellevue, Québec, Canada
[email protected] xv
xvi
Contributors
Yousef Karimi-Zindashty Department of Food Science Macdonald Campus of McGill University Ste Anne de Bellevue, Québec, Canada
[email protected] Michael Ngadi Department of Bioresource Engineering McGill University Montréal, Québec, Canada
[email protected] Stefan Kasapis School of Applied Sciences RMIT University Melbourne, Victoria, Australia
[email protected] Colm P. O’Donnell Biosystems Engineering, School of Agriculture Food Science and Veterinary Medicine University College Dublin Belfield, Dublin, Ireland
[email protected] Yeting Liu Food Science and Technology Programme Department of Chemistry National University of Singapore Singapore
[email protected] Valérie Orsat Bioresource Engineering Department Macdonald Campus of McGill University Ste Anne de Bellevue, Québec, Canada
[email protected] Andreas Lopata School of Applied Sciences RMIT University Melbourne, Victoria, Australia
[email protected] G. S. V. Raghavan Department of Bioresource Engineering Macdonald Campus of McGill University Ste Anne de Bellevue, Québec, Canada
[email protected] Michele Marcotte Food Research and Development Center Agriculture and Agri-Food Canada St Hyacinthe, Québec, Canada
[email protected] S. H. Rajamohamed Food Research and Development Centre Agriculture and Agri-Food Canada St Hyacinthe, Québec, Canada
[email protected] Ruben Mercade-Prieto Department of Biological Systems Engineering University of Wisconsin-Madison Madison, Wisconsin
[email protected] Hosahalli S. Ramaswamy Department of Food Science Macdonald Campus of McGill University Ste Anne de Bellevue, Québec, Canada
[email protected] A. Muthukumaran Department of Bioresource Engineering Macdonald Campus of McGill University Ste Anne de Bellevue, Québec, Canada
[email protected] M. A. Rao Department of Food Science and Technology Cornell University Geneva, New York
[email protected] Kasiviswanathan Muthukumarappan Department of Agricultural and Biosystems Engineering South Dakota State University Brookings, South Dakota
[email protected] Navin K. Rastogi Department of Food Engineering Central Food Technological Research Institute Council of Scientific and Industrial Research Mysore, India
[email protected] or
[email protected] xvii
Contributors
Syed S. H. Rizvi Department of Food Science Cornell University Ithaca, New York
[email protected] Jordi Salazar Sensor Systems Group Department of Electronic Engineering Universitat Politècnica de Catalunya Barcelona, Spain
[email protected] Rakesh K. Singh Food Science and Technology Department The University of Georgia Athens, Georgia
[email protected] Rekha S. Singhal Department of Food Engineering and Technology Institute of Chemical Technology Matunga, Mumbai, Maharashtra, India
[email protected] Litha Sivanandan Reseach and Development Food Technologist Oceana Foods Shelby, Machigan
[email protected] Jirarat Tattiyakul Department of Food Technology Faculty of Science Chulalongkorn University Bangkok, Thailand
[email protected] B. K. Tiwari Biosystems Engineering, School of Agriculture Food Science and Veterinary Medicine University College Dublin Dublin, Ireland
[email protected] Antoni Turó Sensor Systems Group Department of Electronic Engineering Universitat Politècnica de Catalunya Barcelona, Spain
[email protected] Alan O. Wright US Army Natick Soldier R, D & E Center Natick, Massachusetts
[email protected] Jun Xue Food Research Center Agriculture and Agri-Food Canada Guelph, Ontario, Canada
[email protected] David Young School of Biomolecular and Physical Sciences Griffith University Brisbane, Australia
[email protected] Mohammad R. Zareifard Food Research and Development Center Agriculture and Agri-Food Canada St Hyacinthe, Québec, Canada
[email protected] Weibiao Zhou Food Science and Technology Programme Department of Chemistry National University of Singapore Singapore
[email protected] Songming Zhu College of Biosystems Engineering and Food Science Zhejiang University Hangzhou, Zhejiang, People’s Republic of China
[email protected] and 1 Introduction Plan of the Book Jasim Ahmed
Polymer Source Inc.
Hosahalli S. Ramaswamy
Macdonald Campus of McGill University
Stefan Kasapis RMIT University
Joyce I. Boye
Agriculture and Agri-Food Canada
Contents References...........................................................................................................................................6 The growth of novel processing technologies has now become extremely commercially important, involving many new products, industrial collaborations, and academic research groups. This book covers the present status and future trends of novel technologies alongside major lines of development in relation to rheological and functional properties of food. It is important to recognize that developments in novel food processing have mostly taken place in developed countries, however developing countries could benefit from the knowledge already generated in the field. The advantages of novel processing technologies over conventional protocols are the retention of sensory attributes, desired texture, and improved functional properties by focusing on the promising areas of next-generation food processing. Novel technologies can be classified into two categories: electrotechnologies (pulse electric field, radio-frequency (RF) heating, microwave heating, infrared heating, ohmic heating, etc.) which make use of novel methods of heating, and nonthermal technologies (pulse-light, high hydrostatic pressure, oscillating magnetic field, irradiation, ozonization, plasma, osmotic treatment, etc.). Most of the electrotechnologies focus on novel approaches to generate heat and rely on conventional thermal mechanisms for achieving preservation and processing. Nonthermal processing technologies, on the other hand, inactivate enzymes and microorganisms, and modify the functional properties of food by alternate means without substantially increasing the product temperature. The majority of the literature on this subject is devoted to equipment design and process optimization, in conjunction with microbial aspects and safety of various foods. There is, indeed, an urgent need to study microbial survival and destruction under the novel and alternate processing technologies to achieve food sterility or food safety. On the other hand, structural modifications and functionality of ingredients and formulations under novel processes cannot be neglected since they 1
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Novel Food Processing: Effects on Rheological and Functional Properties
have a profound effect on both sensory and nutritional aspects of food. The current emphasis on health-related functional foods leading an integration of food production, processing/preservation, and nutritional aspects has led to renewed interest in the texture and functional properties of materials under novel processing technologies. Structural and functional properties are important determinants of food quality, as perceived by consumers and required by the food industry. Rheology deals with establishing predictions of mechanical behavior based on the micro- or nanostructure of the material, e.g., the molecular size and architecture of food polymers in solution or particle size distribution in a solid suspension. Rheological measurements are essential tools in the analytical laboratory for characterizing component materials and finished products, and monitoring process conditions, as well as predicting product performance and consumer acceptance. Thus, rheological properties provide fundamental insights into the structural organization of food. For example, starch/protein dispersions converted to gel under novel processing exhibit a true viscoelastic nature (Molina, Defaye, and Ledward 2002; Ahmed et al. 2007). In addition, the functionality of food is improved significantly with a novel processing technology like high pressure (HP), which can partially reduce allergenic proteins in rice (Kato et al. 2000), and pulse electric field, which inactivates undesirable enzymes (pectin methyl esterase [Yeom et al. 2002], polyphenol oxidase [Giner et al. 2002], and alkaline phosphatase [Castro 1994]). Frequently, the academic study of food structure is conducted in isolation from the wider commercial and consumer context. A major objective of this book, therefore, is to analyze changes in food structure at the micro- and macromolecular levels when subjected to novel processing technologies and to discuss food properties within this wider context. The contributions culminating in the present form of the book are briefly surveyed in this opening chapter so that readers can readily obtain an overview of the book and its highlights. There are 22 chapters in total, covering most of the novel technologies. It is worth mentioning that a few of the novel processing technologies have been explored mainly for their role in preservation and processing and there is not much information on their effect on rheology/texture and/or functional properties, e.g., pulsed light or pulsed electric field (PEF), and, in these cases, the focus lies on technology rather than core content. RF dielectric heating has been used for decades in thermal processing of nonconductive materials with industrial applications for drying of wood and tempering of frozen foods. RF is promising for many heating and drying processes but there is still a need for more readily available data related to the design of the applicators, targeted product formulations with specific dielectric properties, and control systems for the development of RF heating process applications. Selection of dielectric energy input and its combination with conventional thermal technologies may lead to products that meet and often improve the quality requirements of existing food products, hence opening the field for product development. RF heating applications are focused on in Chapter 2. Ohmic heating is an innovative heating technique employed for thermal processing. The food is placed between two electrodes serving as an electrical resistor and an alternating electric current is passed through the circuit. The electrical resistance causes heat to be generated throughout the food matrix in a uniform and volumetric fashion. The electrical energy is directly converted into heat, causing a temperature rise, and depends largely on the electrical conductivity of the product. It is theoretically possible to properly match the electrical conductivity of solid and liquid phase of particulate fluids such that under ohmic heating the particles could heat faster than the liquid. This is a unique feature that has attracted the attention of the industry, academia, and regulatory agencies to permit ohmic heating as a potential source of treatment in aseptic processing of particulate fluids. Chapter 3 highlights the principles and applications of the technique and their influence on food rheology and functional properties. Chapter 4 deals with the application of high electric field (HEF) to food processing, especially drying. HEF technology offers many distinctive advantages over conventional processing methods. One of the major advantages is that there is insignificant change in temperature during processing. As a result, the method can be successfully applied to any temperature-sensitive fresh material to
Introduction and Plan of the Book
3
retain flavonoids. The processing efficiency and capacity mainly depends on the voltage strength used for processing. Though interest in HEF processing is high, the technique is still in its infancy in terms of industrial exploitation. PEF treatment of liquid foods is one of the emerging nonthermal food preservation processes. It can accomplish food preservation with short treatment times and small increases in food temperature, thus, providing an alternative to thermal pasteurization. The exposure of microbial cells to electric field induces transmembrane potential on the cell membrane, which results in electroporation and electrofusion. The generation of PEF requires a system for generating high-voltage pulses and a treatment chamber that converts the pulsed voltage into PEFs. There has been a significant development in the design of PEF systems during the last 20 years. Chapter 5 reviews the various high-voltage pulse generators and the continuous treatment chambers that have been designed and constructed by different research groups. Ultrasound refers to energy generated by sound waves of 20,000 or more vibrations per second. High frequencies in the range of 0.1–20 MHz, pulsed operation, and low power levels (100 mW) are used for nondestructive testing (Gunasekaran and Chiyung 1994). Ultrasonic excitation is being examined for nondestructive evaluation of the internal quality and latent defects of whole fruits and vegetables in a manner similar to the use of ultrasound for viewing the developing fetus in a mother’s womb (Mizrach et al. 1994). Ultrasound could be used in various applications including rheology, texture, and concentration measurements of solid or fluid foods; composition determination of eggs, meats, fruits, vegetables, and dairy products; thickness, flow level, and temperature measurements for controlling several processes; and nondestructive inspection of egg shells and food packages. Two chapters deal with the technology (Chapter 6) and applications (Chapter 7) of the subject. Ionizing radiation (IR) was the first novel technology applied to food products to enhance shelf life, although it was not easy to convince regulatory agencies and consumers of its safety. IR offers various technological benefits by reducing food losses and improving food safety. Irradiation (1.5–7.0 kGy) applied to solid and semisolid food like meat, poultry, seafood, potatoes, and onions confers the same benefits as thermal pasteurization confers on liquids. After decades of extensive research and testing have demonstrated that IR is safe within prescribed doses, it has been permitted by all specialized agencies of the United Nations (WHO, FAO, and IAEA). Chapter 8 of this book is devoted to this area. Ozone has a wide antimicrobial spectrum that, combined with high oxidation potential, makes it an attractive processing option for the food industry. Relatively small quantities of ozone and short contact times are sufficient for the desired antimicrobial effect as it rapidly decomposes into oxygen, leaving no toxic residues in food (Muthukumarappan, Halaweish, and Naidu 2000). The interest in ozone as an antimicrobial agent is based on its high biocidal efficacy and wide antimicrobial spectrum that is active against bacteria, fungi, viruses, protozoa, and bacterial and fungal spores (Khadre, Yousef, and Kim 2001). Ozone is 50% more effective over a wider spectrum of microorganisms than chlorine. It reacts up to 3000 times faster than chlorine with organic materials and produces no harmful decomposition products (Graham 1997). Such advantages make ozone attractive to the food industry and consequently it was declared as Generally Recognized as Safe (GRAS) for use in food processing by the U.S. Food and Drug Administration (FDA) in 1997 (Graham 1997). Chapter 9 provides details on the issue. Most of the proteins form aggregates under many destabilizing conditions, particularly at high temperatures. Further aggregation leads to a solid-like gel of three-dimensional networks. Chapter 10 discusses protein gelation at room temperatures using a two-step process, usually referred to as cold gelation. The first step involves the formation of soluble aggregates, usually with a heat treatment. The final gelation step is commonly achieved following addition of salts or by reducing pH. Studies of cold gelation procedures in emulsions, bead and microcapsule formation, and with polysaccharide mixtures are reviewed. There are several contributions in this book dealing with HP processing and its effect on rheology, structure, and functional properties. The first of them emphasizes the significant interest among
4
Novel Food Processing: Effects on Rheological and Functional Properties
academicians and processors in the technique. In 1899, Japanese researchers attempted HP treatment of food for the first time. The related publication represents the first reported case of reduction of spoilage by means of high hydrostatic pressure. Pioneering work in 1914 reported that pressure could denature egg white (without heat) resulting in an outlook similar but not identical to that of a cooked egg, is also mentioned. Research in the area of HP food processing was further advanced following the work carried out in Japan in the 1980s. Today, HP appears to be a major processing technology and alternative to heat treatment. It has reached the consumer with a variety of products including fruit jams, jellies, sauces, juices, avocado pulp, guacamole, and cooked ham. This year the FDA approved the pressure-assisted thermal sterilization (PATS) process. The effect of high hydrostatic pressure on the rubber-to-glass transformation of biomaterials with potential industrial interest in confectionery formulations is discussed in Chapter 11. Theoretical aspects of the application of HP to the mechanical properties of synthetic and natural polymers are elaborated to offer a sound basis for utilization of the approach in model food systems. The free volume theory in conjunction with the correct pressure dependence of the compressibility coefficient leads to the Fillers–Moonan–Tschoegl equation, which follows the combined thermorheologically and piezorheologically simple behavior of synthetic polymers. This school of thought was considered in the vitrification of high solid biomaterials but it was demonstrated that the time/temperature/ pressure equivalence of synthetic materials is not operational in the glass-like behavior of high sugar systems in the presence of gelatin or gelling polysaccharides. This deviation from the “normal” course is discussed in terms of the irreversible destabilization of intermolecular aggregates that occurs mainly in polysaccharide networks following pressure-induced vitrification. HP treatments influence the functional properties of proteins through the disruption and reformation of hydrogen bonds, as well as hydrophobic interactions and the separation of ion pairs (Hayakawa, Linko, and Linko 1996). After HP treatment rheological properties of protein foods are significantly altered with texture modification. Protein-water dispersion converts to gel that is softer than thermally treated gel, as indicated by small amplitude oscillatory shear (SAOS) measurement. After pressure treatment, the primary structure of proteins remains intact while secondary, tertiary, and quaternary structures are affected to various degrees. Various instrumental techniques (differential scanning calorimetry, Fourier transform infrared spectroscopy, circular dichromism, size exclusion chromatography, and electrophoresis) are commonly employed to detect structural changes after pressurization. Details are available in Chapters 12, 13, and 14. Chapter 13 deals with pressure effect on plant proteins (soybean, rice, wheat, and lentil) whereas Chapter 14 emphasizes the effect on animal proteins. Chapter 15 discusses the distinct conditions of hydrostatic HP processing of starch-water suspensions, dynamic HP homogenization of starch-water suspensions, and hydrostatic HP compression of starch granules at low moisture contents. These processing treatments lead to various effects ranging from pressure-induced gelatinization to structural and functional modifications. It is found that HP compression has a direct impact on the gelatinization behavior of starches with a favorable temperature shift and enthalpy reduction. Application of HP to fruits and vegetables (Chapter 16) has an influence on their texture due to liquid infiltration and gas displacement. Changes such as collapse of air pockets and shape distortion result in tissue shrinkage. In many cases, pressure-treated vegetables did not soften during subsequent cooking, which was attributed to the inaction of pectin methyl esterase (PME) that was only partially activated by pressure. HP has a major effect on the solid–liquid phase transition of water. Pressure shift freezing (PSF) and HP thawing are two major applications with potential benefits in food processes based on this phenomenon. PSF involves cooling the food samples under pressure (usually up to 200 MPa) to just above the freezing point (−20°C) and quickly releasing the pressure to form massive nuclei of ice crystals; the ice crystals are then allowed to grow at atmospheric pressure in a conventional freezer. PSF can thus, have a significant impact on frozen food quality, especially in terms of preserving the texture of frozen thawed foods, which is greatly affected by the conventional freezing techniques. These issues are highlighted in Chapter 17. Overall it can be
Introduction and Plan of the Book
5
concluded that HP is a potential nonthermal alternative in the processing and preservation of fruit and vegetables that allows better retention of organoleptic qualities. A rapid expansion of research and development on novel food processes has taken place in the last 25 years and has resulted in a variety of novel processes; ultimately, the market success of these novel technologies will depend on the acceptability of these processes to consumers. Chapter 18 focuses on sensory and other consumer issues that must be addressed during the development of foods processed by novel technologies and discusses new and evolving methodologies that should be employed to maximize the sensory quality and acceptance of these foods. The soybean processing industry has matured in the last few decades. Wide varieties of nutritional, functional, and therapeutic ingredients are extracted from soybeans and are currently commercially available. Soybeans also contain antinutritional factors such as trypsin inhibitors, phytic acid, and lectins, which require inactivation or removal prior to consumption. In recent years, novel technologies for soybean processing have emerged, which effectively inactivate antinutritional components and can be used to extract soybean components of interest or to modify functionality. Chapter 19 addresses some of the novel techniques in use or under study for the processing of soy foods and soy ingredients and their effects on product quality and functionality. Supercritical fluid extrusion (SCFX) is an elegant new process developed at the cutting-edge interface of supercritical fluid and conventional extrusion technologies. Low-shear and low-temperature processing, formation of highly expanded products with a unique microcellular structure comprising non-porous skin and homogenous cell size distribution, and use of SC-CO2 as a carrier for soluble flavors and an in-line process modifier are some of the defining characteristics of the SCFX process. These make it superior to the conventional high-shear and high-temperature extrusion cooking and puffing processes. Moreover, SCFX allows a high degree of control over the nucleation and cell growth phenomena, thus, imparting great flexibility in the design of microcellular biopolymer foams of desired morphology and properties such as sensory texture, thermal insulation, etc. Details are available in Chapter 20. The continuous-flow high-pressure throttling (CFHPT) process was developed as a means of continuous microbial inactivation of fluid foods (Toledo and Moorman 2000). Throttling valve is a fine restriction such as a partially closed valve or porous plug to control the flow of the fluid through a micrometering valve. CFHPT uses HP (about 310 MPa) to pressurize liquid foods and to continuously throttle the foods from that HP to atmospheric pressure to inactivate microbes and modifying proteins. As the fluid material exits the throttling valve, temperature increases and the product is rapidly cooled and retains sensory quality. The CFHPT system is a continuous system that uses relatively low pressures. Changes in rheological characteristics of liquid foods processed through CFHPT are discussed in Chapter 21. Frying has remained a major cooking technique and fried foods are popular despite health concerns. However, there is a major effort underway to deal with the health issues of frying with the development of novel processing technologies to reduce fat content without sacrificing taste and flavor. One particular issue relates to batters that are important in determining quality and shelf life of coated fried food products. Their formulation and ingredients impact various functionalities in coated products. Good understanding of the roles of the various ingredients and how they interact with each other are vital in designing optimal batters for specific products. Rheological and thermal properties of batters vary with the different types of flours and their combination ratios, and with the different types of hydrocolloids and other ingredients. Careful study and elucidation of these interactions can be used to control batter functionalities, as described in Chapter 22. About 4% of adults and up to 8% of children suffer from some type of food allergy, with foods such as peanuts, tree nuts, wheat, soy, cow’s milk, egg, fish, and shellfish being responsible for over 90% of reactions. While food allergy is reaching epidemic proportions, currently no curative or prophylactic treatments are available. A molecular description of the allergenic components and protein families present in the major allergenic foods is given in Chapter 23. Research into the area of food allergy is complex because allergenic proteins are exposed to digestive processes and
6
Novel Food Processing: Effects on Rheological and Functional Properties
in addition undergo extensive modifications during processing of food. Thermal processing can reduce the allergenicity of certain allergens (e.g., fruits), while roasting in the presence of sugars can dramatically enhance the allergenicity. The effects of modern processing technologies (e.g., HP processing) on allergenicity are discussed as well as opportunities for the food industry to develop successful processing strategies to effectively protect sensitive consumers to prevent unwanted allergen exposure. A number of outstanding scientists were invited to contribute to this book by providing novelties related to their area of research. Their contributions form the backbone of this innovative work. Contributions were specifically requested to address the effects of novel technologies on rheology and functional properties. A few of our contributors faced difficulties in obtaining detailed mechanistic and rheological information for certain novel technologies, e.g., PEF and irradiation. In such cases, general overviews of related food applications are highlighted in order to include these technologies in the work. Overall, the contributions in the book illustrate in a very clear and concise fashion the structure–functionality relationships as affected by novel processing technologies.
REFERENCES Ahmed J., H. S. Ramaswamy, A. Ayad, I. Alli, and P. Alvarez. 2007. Effect of high pressure treatment on rheological thermal and structural changes in Basmati rice flour slurry. Journal of Cereal Science 46 (2), 148–56. Castro, A. J. 1994. Pulsed electric field modification of activity and denaturation of alkaline phosphatase. PhD thesis, Washington State University. Giner, J., M. Ortega, M. Mesegué, V. Gimeno, G. V. Barbosa-Cánovas, and O. Martín. 2002. Inactivation of peach polyphenoloxidase by exposure to pulsed electric fields. Journal of Food Science 67, 1467–72. Graham, D. M. 1997. Use of ozone for food processing. Food Technology 51, 121–37. Gunasekaran S., and A. Chiyung. 1994. Evaluating milk coagulation with ultrasonics. Food Technology 48 (12), 74–78. Hayakawa, I., Y. Y. Linko, and P. Linko. 1996. Mechanism of high pressure denaturation of proteins. Food Science & Technology 29, 756–62. Kato, T., E. Katayama, S. Matsubara, Y. Omi, and T. Matsuda. 2000. Release of allergic proteins from lentil grains induced by high hydrostatic pressure. Journal of Agricultural and Food Chemistry 48, 3124–26. Khadre, M. A., A. E. Yousef, and J. Kim. 2001. Microbiological aspects of ozone applications in food: A review. Journal of Food Science 6, 1242–52. Mizrach, A., N. Galili, D. C. Teitel, and G. Rosenhouse. 1994. Ultrasonic evaluation of some ripening parameters of autumn and winter-grown ‘Galia’ melons. Scientia Horticulturae 56 (4), 291–97. Molina, E., A. B. Defaye, and D. A. Ledward. 2002. Soy protein pressure-induced gels. Food Hydrocolloids 16, 625–32. Muthukumarappan, K., F. Halaweish, and A. S. Naidu. 2000. Ozone. In: Natural Food Anti-Microbial Systems. A.S. Naidu, Eds. CRC Press, Boca Raton, FL, pp. 783–800. Toledo, R. T., and J. E. Moorman Jr, J. E., inventors; University of Georgia, assignee. 2000. Microbial inactivation by high-pressure throttling. US patent 6,120,732. Yeom, H. W., Q. H. Zhang, and G. W. Chism. 2002. Inactivation of pectin methyl esterase in orange juice by pulsed electric fields. Journal of Food Science 67, 2154–59.
of Radio-Frequency 2 Effect Heating on Food Valérie Orsat
Macdonald Campus of McGill University
Contents 2.1 Introduction...............................................................................................................................7 2.2 Mechanisms of Radio Frequency (RF) Heating........................................................................8 2.2.1 Dielectric Heating..........................................................................................................8 2.2.2 Temperature Uniformity and Arcing Problems........................................................... 10 2.3 Radio Frequency (RF) Heating Applications.......................................................................... 11 2.3.1 Dielectric Properties of Foods..................................................................................... 11 2.3.1.1 Enhancing the Dielectric Properties............................................................. 12 2.3.1.2 Determining the Dielectric Properties.......................................................... 13 2.3.2 Thermal Treatment of Food Products......................................................................... 13 2.3.2.1 Radio Frequency (RF) Inactivation of Microorganisms.............................. 13 2.3.2.2 Radio Frequency (RF) Heating Behavior and Rheology.............................. 14 2.3.2.3 Radio Frequency (RF) Cooking and Enzymatic Inactivation...................... 15 2.3.2.4 Radio Frequency (RF) Drying...................................................................... 16 2.4 Conclusions.............................................................................................................................. 16 Nomenclature.................................................................................................................................... 16 References......................................................................................................................................... 16
2.1 INTRODUCTION The food industry is in continuous flux to meet market demands for healthy, preservative-free, high-quality, and safe food products. Processing technologies being used to ensure food quality and safety are freezing, thermal processing, sterilization, drying, refrigeration, and the controlled distribution of fresh produce. In some applications, dielectric heating/sterilization can deliver highquality products since electromagnetic waves are able to heat the product 3–5 times faster than conventional sterilization systems (Rosenberg and Bögl 1987). The dielectrically heat-treated product is not temperature-abused due to the reduction in process time, so the food has better overall quality attributes than products processed by other available thermal technologies. Microbial and pest reduction by dielectric heating has been well studied for several products including meat and meat products, poultry, eggs, fish, fruit and vegetable products, ready-cooked meals, milk and milk products, cereals, and spices (Harlfinger 1992; Rosenberg and Bögl 1987; Wang et al. 2003b; Lagunas-Solar et al. 2005). Wang et al. (2003b) studied the radio-frequency (RF) sterilization of a model food and macaroni and cheese. Their findings showed that the RF process (27.12 MHz) produced better-quality products, at a faster rate, while using less energy than the conventional retort process used to produce shelf-stable foods. However, conventional cooking and heating techniques generally yield lower microbial counts than microwave/RF treatments when the process is controlled by temperature only (Rosenberg and Bögl 1987). Speed and evenness of heating are influenced by the composition and mass of the food as well as by features of the heating 7
8
Novel Food Processing: Effects on Rheological and Functional Properties
unit. Since the heating during dielectric cooking could be uneven, the presence of relatively cool regions might account for the survival of bacteria even when very high temperatures are recorded in other parts of a food. Many biological materials are color sensitive to temperature, and rigorous temperature control must be maintained to preserve the appearance of the material. Temperature excesses or extended periods of time at tolerable temperatures may change the appearance, taste, or quality of the food product. Research on mutual interactions between food products and dielectric processing equipment is still needed to provide a practical basis for process control and minimizing process energy costs, while ensuring microbial safety and overall product quality.
2.2 MECHANISMS OF Radio Frequency (RF) HEATING 2.2.1 Dielectric Heating Dielectric heating lies in the electromagnetic spectrum range of frequencies from 300 kHz to 300 GHz (Table 2.1). Radio frequencies range from 300 kHz to 300 MHz and microwaves range from 300 MHz to 300 GHz (Assenheim et al. 1979). There are differences in the electrical and thermal responses of foods to microwave and RF fields, which depend on aspects of chemical composition, physical structure, and geometry of the product (Mudgett 1985). The choice of processing frequency in RF or microwave, for a particular unit operation, may be critical since the dielectric behavior and heating characteristics of foods vary with frequency, temperature, moisture, and salt contents. Ionic losses for a particular product may be much higher and dipole losses much lower at 27.12 MHz than at 2450 MHz and vice versa. In a RF heating system, the RF generator creates an alternating electric field between two electrodes. The material to be heated is placed between the electrodes where the alternating electric energy causes polarization, where the molecules in the material continuously reorient themselves to face opposite poles (Figure 2.1). TABLE 2.1 Dielectric Heating Frequency Ranges 300–3000 kHz 3–30 MHz 30–300 MHz 300–3000 MHz 3–30 GHz 30–300 GHz
+
–
+
Medium frequency (MF) High frequency (HF) Very high frequency (VHF) Ultra high frequency (UHF) Super high frequency (SHF) Extremely high frequency (EHF)
–
+ –
Alternating
+
E-field
–
+
+
–
+
–
+ + –
–
+
–
+
–
+
+ +
+
–
–
–
–
+
–
Space charge +
+
+
–
–
Dipolar –
+
–
+
FIGURE 2.1 Space charge and dipolar polarization in between RF electrodes applying an alternating electric field.
Effect of Radio-Frequency Heating on Food
9
With an electric field alternating at the 27.12 MHz radio frequency, the electric field alternates 27,120,000 cycles per second. The energy release resulting from the movement of the molecules and the space charge displacement causes the material to rapidly heat throughout. The amount of heat generated in the product is determined by the frequency, the square of the applied voltage, dimensions of the product, and the dielectric loss factor of the material, which is essentially a measure of the ease with which the material can be heated by RF energy. It is the composition of the material that governs its dielectric properties. The principle of dielectric heating is described by the general expressions for time rate of temperature rise and power dissipation in a dielectric material:
dT P = 0.239 × 10 −6 dt cρ
(2.1)
P = 2 πfE 2ε oε ′′
(2.2)
and
which yields the following equation, since εo = 8.85×10 –12 F/m:
P = 55.61 fE 2ε ′′ × 10 −12,
(2.3)
where dT/dt is expressed in degrees Celsius per second, P is the power (W/m3), c represents the specific heat of the dielectric material (J/kg⋅K), ρ is the density of the material (kg/m3), f is the frequency (Hz), E is the electric field strength (V/m), and ε″ is the dielectric loss factor of the material. When a mixture of materials is subjected to dielectric heating by high-frequency or microwave electric fields, the relative power absorption will depend upon the relative values of E and ε″ for each of the materials in the mixture (Nelson 1985). Too high a value of ε″ results in a skin effect, which annuls the desirable volumetric heating effect. On the other hand, too low an ε″ renders the material practically transparent to the incoming energy. Experience has shown that materials with an effective loss factor in the range 102
