Third Edition FUNDAMENTAL FOOD MICROBIOLOGY Bibek Ray CRC PRESS Boca Raton London New York Washington, D.C. This edition published in the Taylor & Francis e-Library, 2005. “To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.” Cover Image: Microscope with easy phase contrast, dark field, and bright light facilities (M 4002 D). (Courtesy of Swift Instrument International, S.A.) Library of Congress Cataloging-in-Publication Data Ray, Bibek Fundamental food microbiology / Bibek Ray. --3rd ed. p. cm. Includes bibliographical references and index. ISBN 0-8493-1610-3 1. Food--Microbiology. I. Title QR115.R39 2003 664d.001d579--dc22 2003055738 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. 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Visit the CRC Press Web site at www.crcpress.com © 2004 by CRC Press LLC No claim to original U.S. Government works International Standard Book Number 0-8493-1610-3 Library of Congress Card Number 2003055738 ISBN 0-203-99825-1 Master e-book ISBN Dedication To my parents, Hem and Kiron, and my family Preface to the Third Edition In the third edition, substantial changes have been made in most of the chapters and in their logical arrangement. In addition, one new chapter has been added. The chapter on microbial stress has been written to include various manifestations of bacteria under stress and their importance in food microbiology. As before, this book is written primarily for students taking undergraduate food microbiology courses. However, it can be used as a reference in other related courses in many disciplines as well as by professionals engaged directly and indirectly in food-related areas. I thank Elizabeth Smith for her excellent typing and editing in the preparation of the manuscript. Finally, I thank my students for their helpful suggestions, especially for the new materials included in this edition. Preface to the First Edition Between the time I first studied food microbiology as an undergraduate student and now, the discipline has undergone a radical change. This change is well expressed by Dr. David Mossel of the Netherlands in his letter published in ASM News (59, 493, 1993): from “no challenge in plate count and coliform scouting” to “linkage of molecular biology to food safety (also food bioprocessing and food stability) strategies — proclaim a new era in food microbiology.” This transition was necessary to meet the changes that occurred in the food industry, especially in the U.S. and other developed countries. The necessary knowledge, techniques, and expertise for this transition were available. This book reflects this transition from the traditional approach to an approach to meet the needs of those who are directly or indirectly interested in food microbiology. Introductory food microbiology is a required course for undergraduates majoring in food science. In some form it is also taught in several other programs, such as microbiology, public health, nutrition and dietetics, and veterinary science. For the majority of food scientists, except those majoring in food microbiology, this single course forms the basis of the study of microorganisms and their interactions to food. Similarly, for the latter group, food microbiology is probably the only course that provides information on the interaction of food and microorganisms. This book was written with the major objective of relating interaction of microorganisms and food in relation to food bioprocessing, food spoilage, and foodborne diseases. Thus, it will be useful as a text in the introductory food microbiology courses taught under various programs and disciplines. In addition, it will be a valuable reference for those directly and indirectly involved in food and microbiology, including individuals in academic institutions; research institutions; federal, state, and local government agencies; food industries; food consultants; and even food lobbyists. The subject matter is divided into seven sections. For undergraduate teaching, the first six sections can be taught as a semester course; Section VII (Appendices) can be used as advanced information for an undergraduate course which contains materials that are either taught in other courses, such as advanced food microbiology, or food safety courses and laboratory courses. Section I describes the history of food microbiology, characteristics of microorganisms important in foods, their sources, and significance. Section II deals with microbial growth and metabolism of food, and the significance of microbial sublethal injury and bacterial sporulation in foods. Section III explains the different beneficial uses of microorganisms, which include starter cultures, bioprocessing, biopreservation, and probiotics. Section IV deals with spoilage of foods by microorganisms and their enzymes and methods used to deter- mine food spoilage. In addition, there is a chapter on problems and solutions of some emerging spoilage bacteria in refrigerated foods. Section V deals with food- borne pathogens associated with intoxication, infections, and toxicoinfections and those considered to be opportunistic pathogens, as well as pathogenic parasites and algae. In addition, a chapter has been included on emerging pathogens and a chapter on indicators of pathogens. Section VI discusses different methods used to control undesirable microorganisms for the safety and stability of food. A chapter on new nonthermal methods and a chapter on the hurdle concept in food preservation are included. The materials in each chapter are arranged in logical, systematic, and concise sequences. Tables, figures, and data have been used only when they are necessary for better understanding. At the end of each chapter, a limited list of selected references and suggested questions have been included. To reduce confusion, espe- cially for those not familiar with the constant changes in microbial genera, three first letters have been used to identify the genus of a species. The index has been prepared carefully so that the materials in the text can be easily found. I thank Mrs. Deb Rogers for her excellent performance in typing the manuscript. Finally, I thank my students, who, over a period of the last 20 years, have suggested what they would like to have in a food microbiology course. Their suggestions have been followed while writing this text. Preface to the Second Edition It is gratifying to find that CRC Press showed interest in a second edition within 3 years of the initial publication of Fundamental Food Microbiology. As indicated previously, this book was written primarily as a text for undergraduate food micro- biology courses. The main objective was to provide basic and applied information in as many areas as possible in about 500 pages. In the second edition, the materials were carefully edited and new information included to keep it up to date. As before, the second edition will be important not only to undergraduate students in a food microbiology course, but also as a valuable reference book to graduate students in the food science area, to individuals associated with the science, application, pro- duction, and regulation of foods as related to microorganisms in academic institu- tions, research institutions, and food-testing laboratories. In addition, short course organizers, food consultants, food industries, food regulatory agencies, and food science professionals will find this book valuable to understand and solve problems associated with microbiological aspects of food. I thank Mrs. Deb Rogers for her excellent typing and editing in the preparation of the manuscript and the students in the food microbiology class for their helpful suggestions, including the new material in the second edition. The Author Bibek Ray, Ph.D., was a professor of food microbiology in the Department of Animal Science at the University of Wyoming, Laramie. Professor Ray earned B.S. and M.S. degrees in veterinary science from the University of Calcutta and University of Madras, in India, respectively. He received his Ph.D. in food science from the University of Minnesota in 1970 and joined the faculty in the Department of Food Science, North Carolina State University, and then the Department of Biology at Shaw University, both at Raleigh. He joined the University of Wyoming in 1981. There he expanded his research to intestinal beneficial bacteria, bacteriocins of Gram-positive bacteria, and high