Effects of Irradiation on Selected Pathogens in Meat and Meat Products An-Hung Fu Iowa State University

Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1994 Effects of irradiation on selected pathogens in meat and meat products An-Hung Fu Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Agriculture Commons, Food Microbiology Commons, Microbiology Commons, and the Radiology Commons Recommended Citation Fu, An-Hung, "Effects of irradiation on selected pathogens in meat and meat products " (1994). Retrospective Theses and Dissertations. 10603. https://lib.dr.iastate.edu/rtd/10603 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. U'M'I MICROFILMED 1994 INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from lefr to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. University Microfilms international A Bell & Howell Information Company 300 North Zeeb Road. Ann Arbor, 1^148106-1346 USA 313/761-4700 800/521-0600 Order Number 9424217 Effects of irradiation on selected pathogens in meat and meat products Fu, An-Hung, Ph.D. Iowa State University, 1994 Copyright ©1994 by Fu, An-Hung. All rights reserved. UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106 Effects of irradiation on selected pathogens in meat and meat products by An-Hung Fu A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Departments: Food Science and Human Nutrition Animal Science Co-majors: Food Science Meat Science Approved: Signature was redacted for privacy. In Qiarge of Major Work Signature was redacted for privacy. For the Major Departments Signature was redacted for privacy. For the Graduate College Iowa State University Ames, Iowa 1994 Copyright © An-Hung Fu, 1994. All rights reserved. ii DEDICATION To my parents, wife, and sons. ill TABLE OF CONTENTS ACKNOWLEDGMENTS vi CHAPTER I. GENERAL INTRODUCTION 1 Dissertation Organization 2 CHAPTER n. LITERATURE REVIEW 3 Food Irradiation 3 History of development 3 Current status of irradiated meat in U.S 6 Irradiation 8 The effects of ionizing radiation on food 11 Dose-rate effects of irradiation 13 Wholesomeness of irradiated meat and meat products 16 Legislation and regulation of food irradiation 25 Advantages 26 Consumer acceptance 28 Important Meat Pathogens 30 Foodbome illness 30 Etiology 31 Economic impact 33 Pathogens of meat 33 General effect of irradiation on microorganisms 34 Listeria monocytogenes 38 Salmonella spp 44 Yersinia enterocolitica 48 Escherichia coli 0157:H7 53 iv CHAPTER m EFFECT OF IRRADIATION ON SURVIVAL OF SELECTED PATHOGENS AND ON QUALITY ATTRIBUTES OF COOKED PORK CHOPS AND CURED HAM 59 Abstract 59 Introduction 59 Materials and Methods 62 Sample preparation 62 External inoculation and packaging 63 Irradiation 64 Physical and chemical analyses 65 Microbiological analyses 65 Sensory color and odor evaluation 66 Statistical analyses 67 Results and Discussion 68 Effects of dose-rate on microorganisms and quality attributes 68 Effects of irradiation on microorganisms 68 Effects of irradiation on quality attributes 72 Conclusions 74 References 75 CHAPTER IV. EFFECT OF IRRADL\TION ON SURVIVAL OF SELECTED PATHOGENS AND ON QUALITY ATTRIBUTES OF BEEF LOINS, STEAKS, AND GROUND BEEF 87 Abstract 87 Introduction 87 Materials and Methods 90 Sample preparation 90 External inoculation and packaging 90 Irradiation 91 Physical and chemical analyses 92 Microbiological analyses 93 V Sensory color and odor evaluation 94 Statistical analyses 94 Results and Discussion 95 Effects of dose-rate on microorganisms and quality attributes 95 Effects of irradiation on microorganisms 96 Effects of irradiation on quality attributes 101 Conclusions 102 References 103 CHAPTER V. GENERAL CONCLUSIONS 118 LITERATURE CITED 120 vi ACKNOWLEDGMENTS I would like to thank Dr. Joseph G. Sebranek for his guidance over the last six years as my major professor. Dr. Sebranek has allowed me great freedom on academic work and research, and providing ideas and timely suggestions. Thanks are due to Dr. Eisa A. Murano for professional help when problems arose. I also acknowledge my graduate committee members: Dr. L. A. Wilson, Dr. F. C. Parrish, Dr. D. F. Cox, and Dr. C. L. Tipton, for their patience and encouragement throughout my Ph.D. study. I would like to express my gratitude to the faculty and staff of the Meat Laboratory, Departments of Food Science and Human Nutrition (FSHN), Microbiology, Immunology, and Preventive Medicine (MIPM), and my colleagues in the laboratory, for their consistent help during my stay at Iowa State University. Thanks must go finally to my parents for their care and support; my wife, Jia-Jing Jien and my sons for their patience and encouragement, we together went through delightful days and even the flood '93 right in our apartment! This work was partially supported by the National Live Stock and Meat Board. 1 CHAPTER I. GENERAL INTRODUCTION Food safety is a major concern of consumers and food manufacturers. Beran (1991) stressed that about 25% of foodbome diseases were traced to meat and meat products as sources. Sporadic outbreaks of illness caused from ingesting meat or meat products have evoked wide spread publicity and intensive research on preventing further outbreaks. New technology has modified meat processing procedures, packaging, transportation, and storage methods to provide convenient, various items and also extend shelf-life to gain more profit. Some food pathogens have emerged due to these changes and cause new hazards in these products. Irradiation has been verified as an alternative to decrease microbial load and to eliminate specific pathogens on meat, without changing nutritive and sensory quality. The USDA/FSIS has approved the use of irradiation to reduce bacterial contamination of raw poultry (USDA, 1992a). More research is required for red meats and their products to demonstrate the advantages of irradiation and gain regulatory approval. Irradiation is a promising means to ensure safety of meat and meat products. The purpose of this study was to evaluate the effects of irradiation at low and medium doses, each at different dose- rates for effectiveness on selected pathogens in meat and meat products. Color, pH, lipid oxidation (TEA), and sensory attributes (color and odor) were also monitored. Products used for this study included: "ready-to-eat" pork chops, cured hams, fresh beef loins, steaks, and ground beef. 2 Dissertation Organization A general introduction, pertinent to the whole dissertation is included at the beginning as Chapter 1. Chapter n includes a literature review on food irradiation and important meat pathogens. Two individual manuscripts, which are to be published, are individually designated as Chapter m and Chapter IV; followed by general conclusions as Chapter V. A list of literature cited in the general introduction and literature review is at the end of the dissertation. 3 CHAPTER II. LITERATURE REVIEW Food Irradiation History of development Foods are processed and preserved to increase their variety, palatability, safety, and to extend shelf-life. For many centuries, heating, canning, refrigeration and freezing, dehydration or chemical preservation have been used to fulfill this purpose (Hall, 1989). The form of energy on which the process of food irradiation is based, was discovered just before the start of this century (Dempster, 1985). Irradiation is, therefore, a more recently available means of achieving food preservation. The early discovery of X-rays by W. K. Rontgen in 1895 and the discovery of radioactive substances by H. Becquerel in 1896 laid the foundation for food irradiation. However, at that time facilities were too expensive to consider practical application (Brynjolfsson, 1989). Most food irradiation studies started in earnest shortly after World War n. The impetus to this research resulted largely from intensive investigations of nuclear energy, which led to the economic production of radioactive isotopes and to evolution of high energy

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