71A-5 |
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S. A. IBRAHIM, Food Science and Nutrition Program, North Carolina A&T State Univ., Dept. of Human Environment and Family Sciences, 171-B Carver Hall, Greensboro, NC 27411-1064, R. R. Shaker, Dept. of Nutrition and Food Technology, Jordan Univ. of Science and Technology, Irbid, Jordan, and S. Sukhon, Dept. of Basic Veterinary Medical Sciences, Jordan Univ. of Science and Technology, Irbid, Jordan. E. coli O157:H7, salmonella, and listeria are the major foodborne pathogens that represent the greatest concern to the dairy industry. Practical and efficient intervention techniques are needed for dairy foods during processing to ensure the microbial safety of dairy products. Several food processing methods have been developed to interfere with bacterialhomestasis, prevent growth, or kill foodborne pathogens. Some common hurdles used to control microbial growth are pH, sodium chloride, and storage temperature. The objective of this study was to determine the combined effects of salt, acid, and milk solids on the survival and growth of E. coli O157:H7, Listeria monocytogenes, and Salmonella typhimurium. Batches of tryptic soy broth (TSB) with combinations of sodium chloride (0.0, 1.0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0%), pH (6.5, 6.0, 5.5, 5.0, 4.5, 4.0, 3.5), and milk solids (0.0, 10, 20, 30%) were prepared and inoculated with one of the following foodborne pathogens: E. coli O157:H7 (EC1, EC2), Listeria monocytogenes (LM01, LM02), and Salmonella typhimurium (ST01, ST02). Samples were then incubated at 36 °C for 12 hr and the bacterial populations were determined. Results showed that both E. coli O157:H7 and Salmonella typhimurium were able to survive low pH value (3.5), whereas Listeria monocytogenes was more acid-sensitive. Significant growth reduction was observed with all foodborne pathogens in the presence of sodium chloride concentration 2.0% or higher. The combined effect of salt and acid showed significant growth reduction (< 0.05) with 1% salt and pH 5 (2 to 3 log reduction). Addition of milk solids promotes the growth of the foodborne pathogens. The presence of milk solids significantly enhanced the survival of these pathogens in the presence of high salt and low pH, indicating that milk solids may act as a protective agent against many hurdles. The presence of milk solids could enhance the survival and growth of foodborne pathogens at lower pH and high salt concentrations.
Session 71A, Dairy Foods: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |