Robinson: Modern Dairy Technology: Volume 1 Advances in Milk Processing PDF
Preview Robinson: Modern Dairy Technology: Volume 1 Advances in Milk Processing
MODERN DAIRY TECHNOLOGY Volume 1 Advances in Milk Processing Second Edition MODERN DAIRY TECHNOLOGY Volume 1 Advances in Milk Processing Second Edition Edited by R. K. Robinson Department of Food Science and Technology, University of Reading, UK SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. First edition 1986 Second edition 1994 © 1994 Springer Science+Business Media Dordrecht Originally pub1ished by Chapman & Hall in 1994 Softcover reprint of the hardcover 2nd edition 1994 ISBN 978-1-4613-5853-4 ISBN 978-1-4615-2057-3 (eBook) DOI 10.1007/978-1-4615-2057-3 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the UK Copyright Designs and Patents Act, 1988, this publication may not be reproduced, stored, or transmitted, in any form or by any means, without the prior permission in writing of the publishers, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the-. terms stated here should be sent to the publishers at the London address printed on this page. The publisher makes.no representation, express or implied, with regard to the accuracy of the inforination contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication data available Printed on acid-free text paper, manufactured in accordance with ANSIjNISO Z39.48-1992 (Permanence of Paper). Preface to the First Edition The dairy industry is, in many countries, a major contributor to the manufacturing capacity of the food sector, and as more components of milk are utilised in processed foods, so this importance is likely to grow. Already dairy operations range from the straightforward handling of liquid milk through to the production of highly sophisticated consumer items, and it is of note that all this activity is based on a raw material that is readily perishable at ambient temperatures. This competitive, commercial position, together with the fact that the general public has a high regard for dairy products, is an indication of the extent to which milk producers and processors have combined to ensure that retail prO(;lucts are both nutritious and hygienically acceptable. Achievement of these aims, and at reasonable cost, has depended in large measure on the advances that have been made in the handling of large volumes of milk. Thus, factories designed to handle millions of litres of milk per week are now commonplace, and it is the plant and equipment involved that provides the factual background for this two-volume book. In some instances, the increased capacity has arisen simply from an expansion of a traditional method, but in others a totally new approach has had to be adopted either for the manufacturing process per se, or for utilisation of the end products. Success has also depended on the derivation of accurate process controls, both through automation, and through improved procedures for quality control. Together, these diverse facets make up the modem dairy industry, and it is to be hoped that these two volumes will do justice to the innovative genius of those who have been involved in its evolution. R. K. ROBINSON Preface to the Second Edition Developments in process technology tend to be driven by the aims of improving the efficiency of an existing process, or increasing market share through the manufacture of a new product range. In either situation, the essentials of maintaining product quality and safety remain of paramount importance, and hence the tendency is for processes to evolve rather than emerge de novo. Nevertheless, the changes so introduced can result in significant improvements in, for example, the economics of a particular plant or process, and few manufacturers can afford to ignore trends emerging elsewhere within their sector of the food/dairy industry. Similarly, stu dents of dairy science and technology need to be aware of recent developments, hence the aim of this second edition is to highlight the way in which manufacturing procedures have been modified over the past ten years. Inevitably, some sections of the text have required little modifica tion whereas others have needed extensive alteration but, whichever approach has been employed, this new edition seeks to present a totally up-to-date account of the manufacture of dairy products. R. K. ROBINSON Contents Preface to the First Edition v Preface to the Second Edition vii 1. Heat Treatment of Milk 1 M.1. Lewis 2. Developments in Cream Separation and Processing 61 C. Towler 3. Production of Butter and Dairy Based Spreads 107 R. A. Wilbey 4. Drying of Milk and Milk Products . . . . 159 The late M. E. Knipschildt and G. G. Andersen 5. Protection against Fire and Explosion in Spray Dryers 255 O. Skov 6. Membrane Processing of Milk . . . 273 A. S. Grandison and F. A. Glover 7. Utilisation of Milk Components: Whey 313 J. G. Zadow 8. Utilisation of Milk Components: Casein. 375 C. R. Southward 9. Automation in the Dairy 433 W. M. Kirkland Index. . . . . . . . . 473 List of Contributors G. G. Andersen APV Anhydro AS, 7 f/Jstramarken, DK-2860 S~borg-Copenhagen, Denmark. F. A. Glover Formerly National Institute for Research in Dairying, Shinfield, Reading RG2 9AT. Present address: 39b St Peter's Avenue, Caversham, Reading, Berkshire, UK. A. S. Grandison Department of Food Science and Technology, University of Reading, Whiteknights, Reading RG6 2AP, UK. W. M. Kirkland APV Baker Ltd., PO Box 4, Gatwick Road, Crawley RHlO 2QB, West Sussex, UK. M. E. Knipschildt APV Anhydro AS, 7 f/Jstramarken, DK-2860 S~borg-Copenhagen, Denmark. M. J. Lewis Department of Food Science and Technology, University of Reading, Whiteknights, Reading RG6 2AP, UK. O. Skov APV Anhydro AS, 7 f/Jstramarken, DK-2860 S~borg-Copenhagen, Denmark. C. R. Southward New Zealand Dairy Research Institute, Private Bag, Palmerston North, New Zealand. xii List of contributors C. Towler New Zealand Dairy Research Institute, Private Bag, Palmerston North, New Zealand. R. A. Wilbey Department of Food Science and Technology, University of Reading, Whiteknights, Reading RG6 2AP, UK. J. G. Zadow Formerly Division of Food Research, CSIRO, Dairy Research Laboratory, PO Box 20, Highett, Victoria 3190, Australia. Present address: Z. G. Zadow & Associates, Mordialloc, Victoria, Australia Chapter 1 Heat Treatment of Milk M. J. Lewis Department of Food Science and Technology, University of Reading, UK In this chapter, milk will refer to bovine milk, either as full cream milk, skim-milk obtained by centrifugal separation, or standardised milk made by combining skim-milk with cream. Currently UK milk is not standard ised, although both skim-milk and particularly semi-skim milk contain ing between 1 and 1·5 per cent fat have become more popular. Sales of semi-skim milk have increased from 4·74 million tonne in 1985 to almost 17.7 million tonne in 1990 (a 373 per cent increase). However, this increase has not occurred in other EC countries: France, 10 per cent; Germany, 5·4 per cent; and Netherlands 17·4 per cent. Other types of milk that require heat treatment are flavoured milk, reconstituted milk, filled milk, evaporated milk, milk modified in composition by demineralisation or lactose hydrolysis and protein-enriched milk produced by ultrafiltra tion. Milk from other species, such as goats, sheep and buffalo, may also be very important in some countries. Milk can be regarded as a complete food, containing protein, fat, lactose, vitamins and minerals, together with natural enzymes and those derived from microorganisms within the milk. It has a high nutritional value, but is an excellent medium for microbial growth. Milk is extremely variable in its composition. There are variations between individual cows in a breed, between breeds and between seasons. Variations between species are also very considerable (Jenness, 1982; Walstra and Jenness, 1984). Milk is heated for a variety of reasons. The main reasons are: to remove pathogenic organisms; to increase shelf-life up to a period of six months; to help subsequent processing, e.g. forewarming before 2 M. J. Lewis separation and homogenisation; or as an essential treatment before cheesemaking, yoghurt manufacture and the production of evaporated and dried milk. When milk is heated, many changes take place, Fox (1982) has summarised the changes that may lead to protein coagulation: decrease in pH; precipitation of calcium phosphate; denaturation of whey proteins and interaction with casein; Maillard browning; modification of casein: dephosphorylation, hydrolysis of K-casein and general hydrolysis; changes in micellar structure: zeta potential, hydration changes; association-dissociation. The casein fraction of milk is very heat stable, whereas the whey 0c. protein fraction is heat labile and almost completely denatured at 100 The denatured whey protein complexes with the casein and does not usually precipitate. But when cheese whey is heated, the proteins start to denature, coagulate and precipitate between 75 and 80°C. This illustrates the protective effect of casein toward coagulation. A solution of sodium caseinate can withstand heating at 140°C for longer than 60 min at pH 6·7. Other important changes take place during heating and subsequent storage. They affect the nutritional value and sensory characteristics. Broadly speaking, the two major types of heat treatment are pasteurisa tion and sterilisation. The major concerns about the resulting pro ducts are safety and quality. Heat-treated milk should not be a public health risk. It should have a good keeping quality; provide a good balance of nutrients; and be of desirable sensory characteristics, i.e appearance, colour, flavour and mouthfeel. When milk is heated at a constant temperature, all its constituents and components will be affected, but by different amounts. Increasing the temperature will accelerate reaction rates. But different reactions will be affected to different extents. Physical, chemical, enzymatic and microbial changes will depend principally upon the time-temperature conditions, but will also be influenced by other factors, such as composition, pH, oxygen content and fat globule size. The wide range of reactions taking place when milk is heated will influence the safety and quality of that milk. A brief review is provided of the main kinetic parameters used. The subject is considered in more detail by Kessler (1989) and van Boekel and Walstra (1989).
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