The Technology of Extrusion Cooking

The Technology of Extrusion Cooking

The Technology of Extrusion Cooking Edited by N.D. FRAME Process Development Manager APV Baker Ltd Peterborough SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.

First edition 1994 1994 Springer Science+Business Media Dordrecht Originally published by Chapman & Hali in 1994 Softcover reprint of the hardcover 1 st edition 1994 Typeset in 10/12 pt Times New Roman by Acorn Bookwork, Salisbury, Wiltshire ISBN 978-1-4613-5891-6 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 Glasgow address printed on this page. The publisher makes no representation, express or implied, with regard to the accuracy of the information 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 Cataloguing-in-Publication data The Technology of extrusion cooking / edited by N.D. Frame.-1st ed. p. cm. Includes bibliographical references and index. ISBN 978-1-4613-5891-6 ISBN 978-1-4615-2135-8 (ebook) DOI 10.1007/978-1-4615-2135-8 1. Food-Extrusion. 1. Frame, N.D. TP370.5.T43 1993 664'.02-dc20 93-21259 CIP 8 Printed on permanent acid-free text paper, manufactured in accordance with ANSIINISO Z39.48-1992 (Permanence of Paper)

Preface Extrusion cooking is a specialist area of food technology because of the complexity of the interactive effects which are inherent in the system. General predictive modelling is very difficult because ingredients are diverse and can vary considerably. Modelling tends to be product specific - new product development tends to be by experimental designs and good fortune. The emphasis of this book is on the latest and potential applications of twin screw extrusion in food production, specifically co-rotating intermeshing screw extruders. Of course, in order to develop products and maximise the extruder potential in terms of energy, product quality and output, an overall understanding of the material flow mechanism, barrel fill length and rheology is essential. The book aims to give explanations and general guidance with examples of screw design, configuration and operating parameters for a variety of product categories. It is also intended to help production operators diagnose the symptoms of particular problems such as temperature control, quality variation, raw material inconsistency, etc. For the product development technologist there is more than one way to make a similar product. For example, equipment manufacturers recommend difficult methods for producing flaked corn. In addition, their machines may differ from each other in terms of screw design, power/ volume ratio, screw tip/barrel clearance, etc., making scale-up more problematic. Extruders generate mixing or shear forces in relatively short residence times which make them highly energy efficient in producing, at high outputs, the direct expanded products found in snack and RTE breakfast cereal categories. Unfortunately these shear forces can generate significant heat and physical degradation of ingredients which may be detrimental to quality parameters such as palatability, water absorption, texture or chemical reaction. These factors are especially important to petfood and brewers' hop extrusion. The advantages and limitations of the twin screw extruder are clearly outlined for different categories and the examples provide the necessary information on the practicalities of setting up a new process or widening a current product range. NDF

Contents 1 Operational characteristics of the co-rotating twin-screw extruder 1 N.D. FRAME 1.1 Types of extruders 1.1.1 Single screw 1.1. 2 Co-kneaders 1.1.3 Counter rotating 1.1.4 Co-rotating 1.2 Process characteristics of the t.s.e. 1.2.1 Feeding 1.2.2 Screw design 1.2.3 Screw speed 1.2.4 Screw configurations 1.2.5 Die design 1.2.6 Barrel temperature and heat transfer 1.2.7 Scale-up 1.2.8 Process flow charts 1.3 Ancillary processes 1.3.1 Preconditioning 1.3.2 Devolatilisation 1.4 Raw materials 1.5 Practical operation of the t.s.e.-start up, shut down and control 1.6 Glossary References 1 1 4 4 5 7 7 9 14 17 25 30 35 38 39 39 43 46 48 50 50 2 Raw materials for extrusion cooking processes R.C.E. GUY 2.1 Introduction 2.2n Structure-forming raw materials 2.2.1 Structure-forming raw materials based on starch 2.2.2 Protein-rich raw materials 2.3 Raw materials acting as fillers in the extrudates 2.3.1 Proteins 2.3.2 Starches 2.3.3 Fibrous materials 2.4 Raw materials as plasticisers and lubricants 2.4.1 Water 2.4.2 Oils and fats 2.4.3 Emulsifiers 2.5 Raw materials acting as nucleants for gas bubble formation 2.6 Raw materials acting as flavours 2.6.1 Salt 2.6.2 Sugar References 52 52 55 55 64 66 68 69 69 70 70 70 71

Vlll CONTENTS 3 Breakfast and cereal extrusion technology 73 R.c. MILLER 3.1 Introduction 73 3.2 What is a breakfast cereal? 73 3.3 A closer look at the products 79 3.4 Breakfast cereal processes 80 3.5 Principles of cooking 82 3.6 Overview of cooking processes 86 3.6.1 Boiling water cookers 88 3.6.2 Steam cookers 88 3.6.3 Adiabatic extrusion 89 3.6.4 High shear cooking extrusion 89 3.6.5 Low shear, high pressure cookers 90 3.6.6 Low shear, low pressure cookers 91 3.6.7 Continuous steam pre-cooking 91 3.7 Breakfast cereal processes: traditional and extrusion methods 92 3.7.1 Flaked cereals 92 3.7.2 Extrusion puffed breakfast cereals 99 3.7.3 Oven puffed cereals 101 3.7.4 Gun puffed cereals 103 3.7.5 Shredded products 104 3.7.6 Pre-cooked hot cereals 107 3.8 Conclusion 108 References 108 4 Snack food extrusion 110 G. MOORE 4.1 Introduction 110 4.2 Ingredients 110 4.2.1 Cereals 111 4.2.2 Root crops 112 4.2.3 Process aids 113 4.3 Equipment review 115 4.3.1 Mixing equipment 115 4.3.2 Feeders 116 4.3.3 Conditioning cylinders 116 4.3.4 Extruders 116 4.3.5 Dryers 119 4.3.6 Fryers 119 4.3.7 Coaters 120 4.4 Direct expanded products 121 4.4.1 Process description 121 4.4.2 Fried collets 123 4.4.3 Baked collets 126 4.5 Co-extruded snacks 127 4.5.1 Process description 127 4.5.2 Formulation 131 4.5.3 Miscellaneous 133 4.6 Indirect expanded products 133 4.6.1 Pellets 134 4.6.2 Fabricated chips 136 4.7 Die and cutter design 139 4.7.1 Die plates 139 4.7.2 Die holes 140

CONTENTS IX 4.7.3 Effect of expansion forces 140 4.7.4 Effect of viscoelastic forces 140 References 143 5 Petfood and fishfood extrusion 144 G.J. ROKEY 5.1 Introduction 144 5.2 Raw material characteristics and selection 144 5.2.1 Protein sources 145 5.2.2 Starch sources 147 5.2.3 Fat, fibre and ash consideration 149 5.2.4 Minor ingredients 151 5.2.5 Typical formulations 153 5.2.6 Raw material preparation 155 5.3 Selection of hardware 156 5.3.1 Feeding devices 158 5.3.2 Preconditioning considerations 159 5.3.3 Extruder barrel selection 162 5.3.4 Die/knife design 169 5.3.5 Ancillary process equipment 172 5.4 Processing variables 175 5.4.1 Preconditioning 175 5.4.2 Extrusion 176 5.4.3 Process control 180 5.5 Final product specifications 181 5.5.1 Quality control 181 5.5.2 Troubleshooting techniques 186 5.6 Evaluation of operational costs 187 5.7 Conclusion 188 References 189 6 Confectionery extrusion 190 E.T. BEST 6.1 Introduction 190 6.2 Processing 191 6.2.1 Pre-extrusion processes 191 6.2.2 Cooker extruder profiling 193 6.2.3 Addition and subtraction of materials 196 6.2.4 Shaping and forming at the die 197 6.2.5 Post -extrusion processes 198 6.3 Flavours and other special ingredients for confectionery extrusion 199 6.4 Liquorice 201 6.5 Toffees, caramels and fudges 206 6.6 Boiled sweets 207 6.7 Sugar crust liqueurs 210 6.8 Pressed tablets 210 6.9 Creams, pastes and lozenges 212 6.10 Gums 215 6.11 Jellies 216 6.12 Cocoa and crumb 218 6.13 Chocolate 220 6.14 Reaction chamber products 222 6.15 Aerated confections 223 6.16 Chewing gum 225 6.17 Frozen confectionery 226

x CONTENTS 6.18 Croutons 6.19 Three-dimensional confections 6.20 Confections by half products 6.21 Other areas 6.22 Conclusion Acknowledgements References 7 Extrusion of brewers' hops K.T. WESTWOOD 227 228 230 231 232 233 233 237 7.1 Introduction 237 7.2 Application of extrusion technology to the production of bitterness in beer 238 7.2.1 Background 238 7.3 Development of extrusion technology in hop processing 241 7.4 Process chemistry-choice of alkaline salt 242 7.5 Composition and quality of extruded hops 245 7.6 Experimental brewing studies with extruded hops 246 7.7 Process development to commercial scale production 246 7.8 Conclusion 250 References 250 Index 251

Contributors Mr E.T. Best Westreco Inc., Missouri Development Centre, 3916 Pettis Road, St Joseph, M064593, USA Mr N.D. Frame Dr R.C.E. Guy Mr R.C. Miller Mr G. Moore APV Baker Ltd, Manor Drive, Paston Parkway, Peterborough PE4 7 AP, UK Flour Milling and Baking Research Association, Chorleywood, Herts WD3 5SH, UK RD2 Box 413, Auburn, New York 13021, USA 3200 Fruit Ridge Avenue, NW, Grand Rapids, Michigan 49504, USA Mr G.J. Rokey Wenger Manufacturing, Sabetha, Kansas 66534, USA Dr K.T. Westwood Brewing Research Foundation, Lyttel Hall, Nutfield, Redhill RH14HY, Surrey, UK