Bakery Food Manufacture and Quality. Water Control and Effects

Transcription

1 Bakery Food Manufacture and Quality Water Control and Effects

2 Bakery Food Manufacture and Quality Water Control and Effects STAN LEY P. CAUVAl N and LINDA S. YOUNG Campden & Chorleywood Food Research Association Chipping Campden Gloucester, UK b Blackwell Science

3 by Blackwell Science Ltd Editorial Offices: Osney Mead, Oxford OX2 OEL 25 John Street, London WClN 2BL 23 Ainslie Place, Edinburgh EH3 6AJ 350 Main Street, Malden MA , USA 54 University Street, Carlton Victoria 3053, Australia 10, rue Casimir Delavigne Paris, France Other Editorial Offices: Blackwell Wissenschafts-Verlag GmbH Kurfiirstendamm Berlin, Germany Blackwell Science KK MG Kodenmacho Building 7-10 Kodenmacho Nihombashi Chuo-ku, Tokyo 104, Japan The right of the Authors to be identified as the Authors of this Work has been asserted in accordance with the Copyright, Designs and Patents Act 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, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. First published 2000 Set in loil2pt Times by DP Photosetting, Aylesbury, Bucks Printed and bound in Great Britain by MPG Books Ltd, Bodmin, Cornwall DISTRIBUTORS Marston Book Services Ltd PO Box 269 Abingdon Oxon OX14 4YN (Orders: Tel Fax: ) USA Blackwell Science, Inc. Commerce Place 350 Main Street Malden, MA (Orders: Tel Fax: ) Canada Login Brothers Book Company 324 Saulteaux Crescent Winnipeg, Manitoba R3J 3T2 (Orders: Tel Fax: ) Australia Blackwell Science Pty Ltd 54 University Street Carlton, Victoria 3053 (Orders: Tel Fax: ) A catalogue record for this title is available from the British Library ISBN Library of Congress Cataloging-in-Publication Data Cauvain, Stanley P. Bakery food manufacture and quality: water control and effectsistanley P. Cauvain and Linda S. Young. p. cm. Includes bibliographical references and index. The Blackwell Science logo is a trade mark of Blackwell Science Ltd, registered at the United ISBN Kingdom Trade Marks Registry 1. Baked products. 2. Baking-Quality control. I. Young, Linda S. 11. Title. TX C dc For further information on Blackwell Science, visit our website:

4 Preface 1 Water and its roles in baked products The composition and heat-related properties of water Vapour pressure and relative humidity Water hardness Ionisation and solutions The solubility of solids and their recrystallisation Water of crystallisation Vapour pressure of solutions Osmotic pressure Gases in solution Suspensions Colloidal suspensions Hydration Water as a plasticiser Surface tension and capillary action Gels and emulsions Water in bakery ingredients 2 The role of water in the formation and processing of bread doughs Wheat flour properties The formation of bread doughs Optimum dough water levels Wheat flour water absorption capacity and its determination Water levels in rye bread doughs The effects of other dough ingredients on water levels in bread doughs Dried gluten Salt Sugars Enzymes Other ingredients Water in brews and sponges Other factors affecting the level of water added to doughs Dough and water temperatures xi

5 vi Water, dough rheology and moulding 3 The role of water in the formation and processing of batters, biscuit and cookie doughs, and pastes The formation of cake batters Dissolution and hydration of ingredients in cake batters Water levels in cake batters Flour properties and water levels in cake batters Gases in cake batters Wafer and other batters Control of batter temperatures Batter viscosity and its measurement Formation and processing of biscuit and cookie doughs Formation and processing of short pastry doughs Formation and processing of laminated doughs Biscuit dough and paste rheological properties Compression-extrusion tests Recording dough mixers Load-extension tests Fundamental tests Choux pastries Bakery products not based on flour Baked products Fillings Toppings and icings Marshmallow Jams and jellies The contribution of water during processing, baking, cooling and freezing 72 Water in retarded and frozen fermented, unbaked doughs The influence of moisture on white spot formation during the retarding of fermented doughs The importance of relative humidity during proof of fermented doughs The contribution of water (steam) to expansion and product structure during baking Bread and fermented products Cakes Laminated products Biscuits and pastries Choux pastry Doughnuts

6 vii Wafers Applications of steam during baking Bread Part-baked breads Cakes Choux pastry Rye breads Chinese steamed breads Surface treatments with water and water-based solutions Water and microwave baking Losses of water during baking and cooling Water in frozen bakery products 5 Effects of water on product textural properties and their changes during storage The contribution of product moisture content to baked product character Bread and fermented goods Cakes Pastries and laminated products Biscuits and cookies Loss of product freshness (staling) Changes in bread character during storage Changes in the character of cakes, biscuits and pastries Checking in biscuits and crackers Water and staling in bread Cakes Effects of freezing and thawing on product texture and eating quality Unbaked bread doughs Unbaked cake batters Unbaked pastries Bread Shelling with frozen crusty breads and part-baked products Cakes Composite products 6 Water activity Sources of moisture in bakery products Product moisture content The importance of water activity The link between moisture content and water activity Definitions of water activity and equilibrium relative humidity

7 viii Water activity and microbial spoilage Water activity and the mould-free shelf-life of a product Effects of packaging Water activity and product rancidity The influence of ingredients on water activity Sucrose equivalence 7 Moisture migration and its control in composite products Mechanisms of moisture migration Diffusion Vapour phase transfer Syneresis Fruited cakes and breads Cream cakes Sugar-based toppings Savoury pastry products Sweetened pastry products Using stabilisers to control moisture migration Moisture migration in composite biscuit products The application of moisture barriers Use of packaging materials Moisture migration and product shelf-life Method 1 Method 2 Method 3 8 Methods of determining moisture content and water availability Determination of product moisture content and water activity Measuring moisture content Oven drying methods Air oven drying Vacuum oven drying Electrical methods Electronic moisture meters Nuclear magnetic resonance Near infrared Infrared - direct heating Advanced techniques for moisture measurement Summary of instrument types used for moisture measurement Methods for the calculation of moisture content Methods for the measurement of water activity Psychrometry

8 ix Indicator salts Mechanical methods Dew point Electric and coulometric methods Spectroscopic methods Quartz crystal oscillation Thermal conductivity gas analysis Weight change method Preparing samples for ERH measurement Bread, rolls, plain cakes, biscuits and cookies Swiss rolls Fruit cakes and Christmas puddings Filled products Instrumental measurement of ERH Methods of calculating water activity and ERH Sucrose equivalence method Determining sucrose equivalence data values Calculating ERH using the sucrose equivalence method Sucrose concentration method Other methods for calculating water activity Software to calculate water activity ERH CALCT 9 Strategies for extending bakery product shelf-life Manipulating water activity using ingredients Storage temperature Effects of ph Extending product shelf-life by adjusting water content Changing salt levels Effects of sugars on cake shelf-life Sucrose Other sugars Using humectants Summary of the effects of recipe changes to cake shelf-life Using preservatives Flour confectionery products Fermented products Biscuit products Reducing moisture migration Extending shelf-life by other means Ethanol surface spraying Modified atmosphere packaging Intelligent packaging Packaging before baking

9 x Packaging directly after baking Infrared (IR) and ultraviolet (UV) irradiation, and microwave radiation Index 206

10 Preface Water is an essential component of almost all of the foods that we consume, yet its presence may pass largely unnoticed. We derive considerable quantities of the water that we need to sustain our lives from this hidden water in foods. The original idea for this book came from the running of seminars on water activity in bakery products. Much is known about the contribution of water to food spoilage and how microbial shelf-life can be influenced by restricting water availability. After all, just like us, microorganisms need water to grow and flourish: restrict the availability of the water and you can restrict microbial spoilage. The contribution of water to organoleptic and other bakery food qualities has also been studied and is largely appreciated. As with microbial growth, the availability of water can be used to explain some of the quality changes that were observed during product storage. The role of water as a plasticiser is becoming established and is being used to help explain product structure formation and quality changes during storage. Despite the quantity of knowledge available on water in foods there seemed to be two problems: there is too little understanding or appreciation of the basic and unique properties of water; and while scientific texts on water in foods exist, there are no practical or technical treaties on the role of water in bakery foods. While the safety and quality of water for human consumption is a very important subject, it is not directly addressed in this book. As with many books, the original idea was only part of the story. In putting together an outline for this book we realised that we too had failed to appreciate the underpinning role that water plays in the manufacture of bakery foods. Here was an ingredient that was essential to the quality of the baked product, but its level had undergone a radical change during the baking process. We knew that a higher level of water at the start of baking processes was important in achieving the required final product quality but it was only when we began thinking about this book that we realised just how important the relationship between starting and finishing water levels are. After introducing water, its unique properties and the relevant basic concepts, the next few chapters of this book consider the role that water plays in the transition from ingredient formulation to baked product. In some ways, Chapters 2 to 4 might be described as baking from the point of view of the water, while the importance of water in the context of food safety, quality and shelf-life are considered in detail in Chapters 5 to 9. In many ways water may called the neglected ingredient in baking. There have been many books on the technology of baking in which the role of water

11 xii Preface has been relegated to what might be described as a supporting role. But water has a much bigger part to play in baking than can be described in a few lines and we hope that this book will go some way to redressing the balance in favour of water so that it can take its rightful place as an essential ingredient in baking as in life. Stanley P. Cauvain Linda S. Young