Properties of Water in Foods NATO ASI Series Advanced Science Institutes Series A Series presenting the results of activities sponsored by the NATO Science Committee, which aims at the dissemination of advanced scientific and technological knowledge, with a view to strengthening links between scientific communities The Series is published by an international board of publishers in conjunction with the NATO Scientific Affairs Division A B Life Sciences Physics Plenum Publishing Corporation London and New York C Mathematical and Physical Sciences D Reidel Publishing Company Dordrecht and Boston D Behavioural and Social Sciences Applied Sciences Martinus Nijhoff Publishers Dordrecht/Boston/Lancaster Computer and Systems Sciences Ecological Sciences Springer-Verlag Berlin/Heidelberg/New York E F G Series E: Applied Sciences - No 90 Properties of Water in Foods in Relation to Quality and Stability edited by D Simatos Ecole Nationale Superieure de Biologle Appliquee a la Nutrition et a l'Alimentation Universite de Dijon Dijon, France J.L Multon Institut National de la Recherche Agronomlque Nantes, France 1985 Martinus Nijhoff Publishers Dordrecht I Boston I Lancaster Published in cooperation with NATO Scientific Affairs Division Proceedings of the NATO Advanced Research Workshop on Influence of Water on Food Quality and Stability (ISOPOW III), Beaune, France, September 11-16, 1983 Library of Congress Catalog in Publication Data NATO Advanced Research Workshop on Influence of Water on Food Quality and Stability (1983 Beaune, France) (NATO ASI series Series E, Applied sciences no 90) "Proceedings of the NATO Advanced Research Workshop on Influence of Water on Food Qualtiy and Stability (Isopow III), Beaune, France, September 11-16, 1983"-"Published in cooperation with NATO Scientific Affairs Division." Includes bibliographical references and index Food Water activity Congresses I Simatos, D II Multon, J L (Jean Louis), 1938III North Atlantic Treaty Organization Affairs Division TX553.W3N38 Scientific IV Title ~ Series 1983 664 85-4946 ISBN-13: 978-94-010-8756-8 ISBN-13: 978-94-010-8756-8 e-ISBN-13: 978-94-009-5103-7 001: 10.1007/978-94-009-5103-7 Distributors for the United States and Canada: Kluwer Boston, Inc., 190 Old Derby Street, Hingham, MA 02043, USA Distributors for the UK and Ireland: Kluwer Academic Publishers, MTP Press Ltd, Falcon House, Queen Square, Lancaster LA 1RN, UK Distributors for all other countries: Kluwer Academic Publishers Group, Distribution Center, P.O Box 322, 3300 AH Dordrecht, The Netherlands All rights reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publishers, Martinus Nijhoff Publishers, P.O Box 163, 3300 AD Dordrecht, The Netherlands Copyright © 1985 by Martinus Nijhoff Publishers, Dordrecht Softcover reprint of the hardcover 1st edition 1985 v Assistant Editors J.e Cheftel Laboratoire de Biochimie et Technologie Alimentaire Universite des Sciences et Techniques du Languedoc Montpellier - F H.B Christian Division of Food Research CSIRO - North Ryde - N.S.W - Australia R.B Duckworth Department of Bioscience and Biotechnology University of Strathclyde - Glasgow - Scotland - U.K F Franks Department of Botany University of Cambridge - Cambridge - U.K G.W Gould Unilever Research - Colworth Laboratory Bedford - U.K J Kapsalis U.S Army Natick Research and Development Center Natick - Mass - U.S.A M Karel Department of Nutrition and Food Science Massachusetts Institute of Technology Cambridge - Mass - U.S.A J Kirk Campbell Soup Company Camden - New Jersey - U.S.A M Le Maguer Food Science Department University of Alberta - Edmonton - Alberta - Canada LB Rockland Food Science Research Center Chapman College - Orange - Cal - U.S.A VII Preface Water is recognized as being an important factor in numerous phenomena connected with the quality of food For instance, it plays a part in the textural properties of several commodities Moreover, water is an essential parameter determining the behaviour of food products in the course of many processing operations : on water, will depend the amount of energy necessary for freezing or dehydrating the product; water will strongly influence the evolution of physical, chemical and biochemical phenomena taking place in the product during processing operations such as heating, drying, etc Water will also influence the same reactions, as well as the activity of microorganisms, during the storage of food products under various conditions As a result, all aspects of quality - sensory, nutritional and hygienic properties of the food - will be affected In all these circumstances, the water content of a product is obviously an important factor, but equally important may be the physical properties of this water, such as its thermodynamic activity and its mobility Actually, the concept of water activity (a ) is now widely used by the food industry and in the legislation of sever')¥l countries The idea of a small, international meeting devoted to a synthetic review and discussion of knowledge on these various matters, was first developed by Dr R.B Duckworth who organized the symposium entitled: Water Relations of Foods, held at the University of Strathclyde (Scotland) in September 1974, under the auspices of Internatioral Union of Food Science and Technology (IUFoS T) The proceedings , edited by R.B Duckworth, still serve as a useful source of reference material for any food scientist or technologist concerned with the subject A second international conference (ISOPOW II), also sponsored by IUFoS T, was organized to complement and supplement information reported in Glasgow and was held in Osaka (Japan) in September 1978 Contributions from Japanese scientists, who have had a traditional interest in the preservation of foods through control of their water content and water activity, introduced valuable new information The proceedings3 were edited by L.B Rockland and G.F Stewart The third symposium of the series (ISOPOW III) was held in Beaune (France) in September 1983 As for the previous meetings, the underlying VIII objective in designing the programme was to examine the relevance of recent advances in fundamental knowledge on the subject to practical problems, as they appear in the industrial processing of foods A very large amount of work has been devoted to the physical properties of water in foods, or more generally in biological systems These properties are commonly considered to play a major, even somewhat magic, role in the structure and functioning of these materials The now classical concept of "bound water" can, however, now be replaced by a more precise description of the state of water thanks to the various physico-chemical techniques presently available The first objective then of ISOPOW III was to review the more recently acquired knowledge concerning the properties of water in food materials and to reevaluate the roles of water in phenomena of interest to the food scientist Sorption phenomena still receive special attention and it was appropriate to consider recently developed isotherm equations and some novel experimental data on sorption hysteresis A better understanding of the effects of water on various phase transitions and reactions which can take place in food products at low and intermediate moisture is highly desirable; The importance of the mobility that water may impart to solutes and the effects of other possible mechanisms were discussed Several non-equilibrium phenomena of great significance for the food industry were considered: superficial water activity, diffusion of solutes and retention of aroma, rheology of hygroscopic powders, effectiveness of packaging Although it may be argued that regarding "the cell as a simple osmometer" is a "gross over-simplification", food microbiologists find the water activity concept extremely valuable as a determining factor for microbial activity It was thus appropriate to again review the present state of knowledge on the ways water may control the activity of microorganisms Then, the combined effects of a and other environmental factors on survival, growth and activity of s'i¥veral types of microorganisms were described, this knowledge being the basis for the promising concept of "hurdles technology" which recently appeared and is being increasingly more widely employed Intermediate moisture foods (IMF) and other water actIvIty - or moisture - adjusted foods receive an increasing interest from the food industry and a session of ISOPOW III was devoted to various practical aspects of this question: evaluation of the water binding power of macromolecules, new humectants, manufacturing aspects Influences of water on quality in certain specific commodity groups were treated: diffusion of water and solutes during processing and storage of fish ; the water binding capacity of meat ; relationships between composition, texture, microbial growth and a in cheese ; prediction of a in confectionery and sugar products w w IX The freezing behaviour of water is a matter of prime importance in a meeting like ISOPOW : the behaviour of water at low temperatures is generally illuminating with regard to the state of water in the system considered ; a better knowledge of this behaviour will also permit optimization of the freezing process for the preservation of foods and also for the less well-known but interesting technique of freeze-texturing Finally, the important practical problems of moisture determination was approached with a comparison of sensors for the measurement of air humidity and a presentation of the results obtained in the course of a collaborative European project (COST 90) aimed at developing a standard method of isotherm determination Water Relations of Foods, 1975, R.B Duckworth, ed., Acad Press, 716 p International Symposium on the Properties of Water Water Activity : Influences on Food Quality, 1981 L.B Rockland and G.F Steward, eds., Acad Press, 921 p Acknow ledgments The symposium was held under the auspices of the International Union of Food Science and Technology (IUFoST) and of the Commission Internationale des Industries Alimentaires It was allocated a grant from NATO, as an Advanced Research Workshop Financial support was received from the following French agencies: Ministere de l'Education Nationale, Ministere de l'Industrie et de la Recherche, Direction des Industries Alimentaires et Agricoles, Institut National de la Recherche Agronomique, Conseil Regional de Bourgogne The following companies also financially contributed to the organization of, ISOPOW III : Allied Grocery Products, Arnott's Biscuits Pty Ltd, ¥s'~ Boake Allen Australia Ltd, Cadbury Schweppes Pty Ltd, Cottee's Gener~l Foods Ltd, CSR Ltd, Sugar Division, H.J Heinz Co Australia Ltd,