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PRINCIPLES OF FOOD PROCESSING
Food Science Texts Series
Series Editor Dennis R. Heldman, University of Missouri
Editorial Board
Richard W. Hartel Hildegarde Heymann
Joseph H. Hotchkiss
James M. Jay
Kenneth Lee Steven J. Mulvaney
Merle D. Pierson
J. Antonio Torres
Edmund A. Zottola
University of Wisconsin
University of Missouri
Cornell University
University of Nevada
Las Vegas
Ohio State University Cornell University
Virginia Polytechnic Institute and State University
Oregon State University
University of Minnesota
Dennis R. Heldman and Richard vv. Hartel, Principles of Food Processing
FOOD SCIENCE TEXTS SERIES
Cameron Hackney, Merle D. Pierson and George J. Banwart, Basic Food Microbiology, 3rd Edition (1998)
James M. Jay, Modem Food Microbiology, 5th Edition (1996)
Harry T. Lawless and Hildegarde Heymann, Sensory Evaluation oj Food: Principles and Practices (1997)
Norman G. Marriott, Essentials oj Food Sanitation (1997)
S. Suzanne Nielsen, Food Analysis (1998)
Norman N. Potter and Joseph H. Hotchkiss, Food Science, 5th Edition (1995)
Romeo T. Toledo, Fundamentals oj Food Process Engineering, 3rd Edition (1998)
Vickie A. Vaclavik, Essentials oj Food Science (1997)
Ernest R. Vieira, Elementary Food Science, Fourth Edition (1996)
PRINCIPLES OFFOOD PROCESSING
DENNIS R. HELDMAN UNIVERSITY OF MISSOURI
RICHARD W. HARTEL UNIVERSITY OF WISCONSIN
A Chapman & Hall Food Science Book
An Aspen Publication Aspen Publishers, Inc.
Gaithersburg, Maryland 1998
The author has made every effort to ensure the accuracy of the information herein. However, appropriate information sources should be consulted, especially for new or unfamiliar procedures. It is the responsibility of
every practitioner to evaluate the appropriateness of a particular opinion in in the context of actual clinical situations and with due considerations to new developments. The author, editors, and the publisher cannot be
held responsible for any typographical or other errors found in this book.
Aspen Publishers, Inc., is not affiliated with the American Society of Parenteral and Enteral Nutrition.
Library of Congress Cataloging-in-Publication Data
Heldman, Dennis R. Principles of food processing.-Dennis R. Heldman and Richard Hartel.!
p. cm.-{Food science text series)
Originally published: New York: Chapman & Hall, 1997. Includes bibliographical references and index.
(Formerly published by Chapman & Hall, ISBN 0-412-99451-8) ISBN 0-8342-1269-2
1. Food industry and trade. I. Hartel, Richard W., 1951- II. Title. III. Series TP370.H44S 1997
664--dc21 97-1648
CIP
Cover design: Will T. Comellas, A.G.T. Inc. Copyright © 1997, 1999 by Aspen Publishers, Inc. All rights reserved.
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Editorial Services: Ruth Bloom Library of Congress Catalog Card Number: 97-1648
ISBN: 0-8342-1269-2
1 2 3 4 5
To
Lou Ann Campbell
Brian Heldman
Paula McMahon
Annakate Hartel
Scott Hartel
CONTENTS
Preface XI
CHAPTER I INTRODUCTION 1
The Food Processing Industry 1
History of Food Processing 3 Processing Concepts 4 General Processing Concepts 7
Kinetics of Quality Change 10
Summary 11
References 12
CHAPTER 2 THERMAL PROCESSING PRINCIPLES 13
Influence of Elevated Temperatures on
Microbial Populations 14
Establishment of Product Shelf-Life and/or Safety 21
Influence of Thermal Process on Product Quality 24
Introduction to Process Calculations 28
References 33
vii
viii CONTENTS
CHAPTER 3 PASTEURIZATION AND BLANCHING 34
Purpose of the Processes 34
Description of Processing Systems 35
Establishment of the Pasteurization Process 45
Determination of Blanching Process 49
Processes for Product Quality Improvement 51
Summary 54
References 54
CHAPTER 4 COMMERCIAL STERILIZATION 55
General Concepts 55
Description of Commercial Sterilization Systems 59
Heating and Cooling of Food in a Container 64
Establishment of Process Times 72
The Influence of Commercial Sterilization
on Product Quality 78
Summary 82
References 82
CHAPTER 5 REFRIGERATED STORAGE 83
Introduction 83
General Principles of Refrigerated Storage 87
Control of Microbial Growth During
Refrigerated Storage 96
Deterioration of Product Quality 101
Establishing Shelf-Life in Refrigerated Foods 105
Future Developments 111
References 112
CHAPTER 6 FREEZING AND FROZEN-FoOD STORAGE 113
Description of Food Freezing Systems
Direct-Contact Freezing Systems
116
119
CONTENTS ix
Individual Quick Freezing (IQF) 123
Estimation of Freezing Time 124
Food Freezing and Product Quality 129
Storage of Frozen Foods 131
Summary 136
References 137
CHAPTER 7 LIQUID CONCENTRATION 138
Evaporation 141
Membrane Separations 153
Membrane Systems 163
Cleaning and Sanitation 166
Food Quality in Membrane Operations 167
Freeze Concentration 167
Types of Freeze Concentration Units 169
Economic Design of Freeze Concentration 175
References 176
CHAPTER 8 DEHYDRATION 177
State of Water in Foods 178
Effects of Drying on Product Quality 182
Moisture Sorption and Desorption 182
Rate of Dehydration 184
Factors That Influence Drying 191
Drying Methods 194
Spray Drying 204
Freeze Drying 211
References 218
CHAPTER 9 OTHER SEPARATION PROCESSES 219
Physical/Mechanical Separations
Diffusional/Equilibrium Separations
References
219
232
252
X CONTENTS
CHAPTER 1 0 FOOD EXTRUSION
Extruders and Extrusion Operations
Principles of Extrusion Operations
Effects of Extrusion on Foods
Recent Developments in Extrusion
References
Index
253
257 265 279 283
283
285
PREFACE
The approach to teaching the concepts of food processing to the undergraduate food science major has evolved over the past 40 years. In most undergraduate food science curricula, food processing has been taught on a commodity basis. In many programs, several courses dealt with processing with emphasis on a different commodity, such as fruits and vegetables, dairy products, meat products, and eggs. In most situations, the emphasis was on the unique characteristics of the commodity and very little emphasis on the common elements associated with processing of the different commodities. Quite often the undergraduate student was allowed to select one or two courses from those offered in order to satisfy the minimum standards suggested by the Institute of Food Technologists.
The current 1FT minimum standards suggest that the undergraduate food science major be required to complete at least one food processing course. The description of this course is as follows:
One course with lecture and laboratory which covers general characteristics of raw food materials, principles offood preservation, processing factors that influence quality, packaging, water and waste management, and sanitation. Prerequisites: general chemistry, physics, and general microbiology.
This textbook, Principles of Food Processing, has been developed to respond directly to the topics identified in the proposed food processing course de-
xi
xii PREFACE
scription. Although sufficient flexibility may not exist in all programs, the ideal positioning of this type of food processing course is after the student has taken food chemistry, food microbiology, and food engineering, and prior to the capstone course.
The approach followed in this textbook is on descriptive components of unit operations used in the processing of food. The text material contains both descriptive information and quantitative evaluations of the individual processes. The descriptive information provides the student with background on the process and the impact of the process on food product quality. A quantitative approach assists the student in understanding the ability of the process to achieve the desired result, as well as the consequences of improper operation of the process. The text contains references to different food commodities to ensure that the student gains an appreciation of the relationships between the commodity and the process.
The early chapters of Principles oj Food Processing deal with more traditional operations used to accomplish preservation. After an introduction to establish a broad base for information to follow in the text, the second chapter presents the general concepts associated with thermal processing. The third and fourth chapters deal with specific food preservation processes, including pasteurization, blanching, and commercial sterilization. Two chapters in the text deal with processes using the reduction of temperature to achieve food preservation. A chapter describes the role of refrigeration temperatures to preserve food and extend shelf-life. A separate chapter is devoted to the use of subfreezing temperatures to preserve foods and extend shelf-life. Both chapters discuss the influence of storage temperatures on shelf-life and product quality.
The reduction of water content in a food product is a separate concept in food preservation. Some processes concentrate the product solids in a nearly equal mass of water. These processes are referred to as concentration. The removal of water beyond that achieved by concentration is referred to as dehydration. Dehydration processes result in very-low-moisture products and shelf-stable products for extended periods of time at ambient temperatures. Principles o/Food Processing contains a chapter devoted to extrusion: a relatively new process leading to shelf-stable food products. The final chapter of the text deals with other separation processes. Although these types of operations may not achieve preservation independently, separation is an essential part of several other preservation processes.
It is important to acknowledge the direction provided by previous textbooks on food processing. Physical Principles oj Food Preservation by Karel, Fennema, and Lund provided the early structure for teaching food processing with emphasis on process. More recently, Food Processing Technology by Fellows has provided similar structure, but with emphasis
PREFACE xiii
on a much larger number of individual processes. Principles oj Food Processing has similarities with these previous textbooks but places even greater emphasis on the description of the process, a quantitative understanding of the process design, and the unique emphasis of the process on product quality.
The authors are pleased to have this opportunity to participate in the education of undergraduate food science majors. The information in the textbook is presented in a manner that will encourage the student to begin the integration of previous knowledge in the areas of chemistry, microbiology, and physics into the study of processes utilized to preserve food products. This initial step in integration provides excellent background for the additional integration expected when the students complete the requirements in a capstone course. The increased emphasis on integration in both the food processing course and the capstone course will improve the ability of the student majoring in food science to understand and appreciate the importance of food chemistry, food microbiology, and food engineering as they influence the quality assurance, sensory evaluation, and product development leading to high-quality and nutritious food products.
Many individuals have contributed to the successful completion of this textbook in either a direct or indirect manner. Both authors have had an opportunity to interact with students and faculty colleagues during the development of the information and materials appearing in the text These interactions have been extremely important in the development of the approach followed in the presentation of the various topics. The authors take this opportunity to express their appreciation to everyone who has assisted in making this textbook possible.
Dennis R. Heldman Richard W. Hartel
PRINCIPLES OF FOOD PROCESSING
