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The Associated Growth of Pseudomonas Fluorescens

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THE ASSOCIATED GROWTH OF PSEUDOMONAS FLUORESCENS, ESCHERICHIA COLI AND / OR LACTOBACILLUS PLANTARUM IN ASEPTICALLY-PREPARED FRESH GROUND BEEF AT 7 °C OR AT 4 AND 25 °C OF STORAGE DISSERTATION Presented in Partial Fulfillment of the requirements of the Degree Doctor of Philosophy in the Graduate School of the Ohio State University By Yi-Mei Sun, M.S. ***** The Ohio State University 2003 Dissertation Committee: Prof. Herbert W. Ockerman, Advisor Approved by Prof. John C. Gordon Prof. Curtis L. Knipe ___________________________ Advisor Prof. Ahmed E. Yousef Department of Animal Sciences UMI Number: 3119496 ________________________________________________________ UMI Microform 3119496 Copyright 2004 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ____________________________________________________________ ProQuest Information and Learning Company 300 North Zeeb Road PO Box 1346 Ann Arbor, MI 48106-1346 ABSTRACT This research was conducted to understand the interactions between normal background microorganisms (Pseudomonas and Lactobacillus) and Escherichia coli on solid food such as fresh ground beef. By using aseptically-obtained fresh ground beef as a model, different levels of background bacteria along with different levels of E. coli were inoculated and applied in three experiments at different storage temperatures. In Experiment I, three levels (zero, 3 logs and 6 logs) of Pseudomonas were combined with three levels (zero, 2 logs and 4 logs) of E. coli and stored at 7 ºC for 7 days. One log increase of VRBA (E. coli) counts was observed for treatments with 2 log E. coli inoculation but no changes were found for treatments with 4 log E. coli inoculation during the 7 days storage at 7 ºC. No effects of Pseudomonas inoculation levels on E. coli counts were observed during the 7 days storage at 7 ºC. The same levels (zero, 2 logs and 4 logs) of Pseudomonas were combined with same levels (zero, 2 logs and 4 logs) of E. coli in Experiment II and stored at 4 ºC for 14 days or 25 ºC for 30 hours for a better understanding of bacteria interaction during storage which occurred in Experiment I when the product was stored at 7 ºC. The results indicated Pseudomonas was still the dominating strain in both storage temperatures (4 and 25 ºC) due to their faster growth rate and short lag time. E. coli counts decreased ii until Day 10 and then increased at Day 14 when stored at 4 ºC, but E. coli counts increased until Hour 25 and then decreased at Hour 30 when stored at 25 ºC. Higher Pseudomonas inoculation had higher E. coli counts at 25 ºC storage (due to metabiosis; Gram et al., 2002) but no effects of Pseudomonas on E. coli counts was observed when stored at 4 ºC. Different from Experiment II, an additional background bacterium, Lactobacillus was added to Experiment III. A total of three bacteria strains were used and more interactions were observed only with the dominating strains at both 4 ºC for 14 days and 25 ºC for 30 hours. Pseudomonas dominated at both storage temperatures. Lactobacillus counts did increase at 25 ºC storage but not at 4 ºC storage. Lower E. coli counts were observed with higher Pseudomonas inoculation treatments and E. coli counts decreased with storage time when stored at 4 ºC. E. coli counts increased with storage time when stored at 25 ºC. Both Lactobacillus and E. coli showed higher counts while Pseudomonas was co-existing when stored at 25 ºC. More reductions of E. coli by higher Pseudomonas inoculation were observed in Experiment III but not in Experiment II or I when stored at 4 ºC. This implied that the addition of Lactobacillus had a synergistic effect on reducing E. coli at 4 ºC storage. This also suggested the probability that more strains of background bacteria would result in more interactions between species and probably might have a better inhibition effects on the growth of fecal source bacteria with refrigerated storage. iii Dedicated to my parents, my sisters and friends iv ACKNOWLEDGMENTS I wish to thank my Advisor, Dr. Ockerman, for his encouragement, support, and advice for all these years in OSU. Extended thanks to my committee members, Dr. Yousef, Dr. Gordon and Dr. Knipe for their advice and patience with me through this research. Thanks to my friends who helps me during my PhD study, Anny and Wen, Mary Kay, Felix, Ada and Louis, Leah, Dorothy and Lilian, and William and make this dissertation possible and complete. Many thanks to Yumi and Joe who support me and take care of my cat (Honey) for me. I would like to thank my parents and sisters who support, love and spoil me all these years for who I am even I am far away from home. Finally, I like to thank God for what he has done in my life. v VITA March 27, 1968 ........................................... Born at Taipei, Taiwan 1987 – 1991................................................. B.S. Dept. of Animal Science National Chung-Hsing University Taichung, Taiwan 1991 – 1992................................................. Research Assistant in National Taiwan University Taipei, Taiwan 1992 – 1995................................................. M.S. in Meat Science, Dept. of Animal Science, The Ohio State University 1995 – present ............................................. Graduate Student, Dept. of Animal Science, The Ohio State University PUBLICATIONS Research Publication 1. Master Thesis “The Utilization of Fresh Garlic, Garlic Powder, Garlic Essential Oil In Reduced Nitrite Chinese Style Sausage” June, 1995. vi 2. “Garlic in Chinese Sausage” 2000 by Journal of Muscle Foods, Vol. 11, p35-43. Also published in 41st Annual International Congress of Meat Science and Technology (ICoMST) meeting, 1995, Texas USA *Recent Research Developments in Nutrition research, 1998, The Ohio State University, USA, “Meat Research Efforts”, Vol. 2, p 13-17. * Department of Animal Sciences “Research and Reviews 1999” by Ohio Agricultural Research and Development Center In Partnership with Ohio State University Extension, special circular 168. 3. “Evaluation of Bacterial Contamination in Chinese Style Sausage” March, 1995 by Meat Focus International, p 101-102. 4. “Effects of Ultimate pH and High Post Mortem Temperature on Meat - A Review” 1996 by Meat Focus International, Vol. 5 Part _. 5. “Influence of Vitamin E on Meat Color and Quality – A Review” 1996 by Meat Focus International, Vol. 5 part 5/6. 6. “ The Growth of Pseudomonas fluorescens and Non-Pathogenic E. coli in Aseptically Obtained Fresh Ground Beef Stored at 4ϒC and 25ϒC.” in 48th ICoMST, Rome, Italy. Contributed papers / Poster session 9. Meat Safety, 2002 FIELDS OF STUDY Major Field: Animal Sciences (Meat Science) vii TABLE OF CONTENTS Abstract................................................................................................................. ii Dedication............................................................................................................. iv Acknowledgements............................................................................................... v Vita....................................................................................................................... vi List of Tables ........................................................................................................ xi List of Figures....................................................................................................... xvi Chapters: 1. INTRODUCTION............................................................................................. 1 2. REVIEW OF LITERATURE ............................................................................ 7 2.1 Microorganisms source of meat...................................................... 7 2.2 Present Microbiology concerns of meat products............................ 10 2.2.1 Most common foodborne microorganisms in meat.................. 10 2.2.2 Foodborne pathogens and their virulence factors .................... 19 2.3 Factors influencing bacteria attachment on meat ............................ 21 2.3.1 Meat....................................................................................... 22 2.3.2 Bacteria.................................................................................. 22 2.3.3 Other factors........................................................................... 24 2.4 Methods and applications of inhibiting microorganism growth on meat............................................................................................... 25 2.4.1 Applications of chemical and physical methods...................... 25 2.4.2 Biological methods................................................................. 29 2.5 Issues of bacteria competition in meat ............................................ 31 2.5.1 Competitive exclusion ............................................................ 32 2.5.2 Microbial competition ............................................................ 34 2.6 Microbiology conditions of beef carcasses and raw ground beef..... 35 2.6.1 General microflora conditions of beef..................................... 35 2.6.2 Dominating microflora and their levels on beef ...................... 40 2.6.3 Characteristics of selected dominant microorganisms ............. 41 viii 3. HYPOTHESIS .................................................................................................. 49 3.1 Rationale.......................................................................................
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