29F-21 |
Fate of Listeria monocytogenes in brain heart infusion broth containing combined potassium lactate and sodium diacetate at various temperatures |
K. A. ABOU-ZEID1, K. S. Yoon1, and R. C. Whiting2. (1) Dept. of Human Ecology, Univ. of Maryland, Eastern Shore, 2109 Trigg Hall, Backbone Rd., Princess Anne, MD 21853, (2) Center for Food Safety & Applied Nutrition, U.S. Food & Drug Administration, Office of Plant & Dairy Foods & Beverages, 5100 Paint Branch Pkwy., HFS-300, College Park, MD 20740-3835 Listeria monocytogenes has been recognized as one of the major food born pathogen due to its ability to survive in diverse environmental conditions, such as low pH, pasteurization, and high NaCl concentrations. Due to severity and case-fatality rates of listeriosis in the highly susceptible human populations, the development of control measure for this pathogen is major concern to the food industry. Our objective was to determine the minimum antimicrobial level of PURASAL P Opti. Form 4TM (60% solution, 56% potassium lactate and 4% sodium diacetate) against L. monocytogenes in pH adjusted broth (6.0 and 6.5) at various temperatures. 102 L. monocytogenes Scott A (ATCC 49594) were inoculated into pH-adjusted broth and stored at 4, 10, and 24°C. Appropriate dilutions of broth were enumerated by spiral plating on tryptose agar and counting with an automated colony counter. Growth curves were generated and iteratively fitted using non-linear regression analysis to the Gompertz equation using a GraphPad PRISM®. At 4°C, addition of 1.1 % Opti.Form4TM significantly inhibited the growth of L. monocytogenes in broth at both pHs. Addition of 1.8 % or 2.7 % Opti. Form 4TM fully controlled the growth of L. monocytogenes in broth at pH 6, but not at pH 6.5, indicating that a lower pH enhanced the antilisterial activity of Opti.Form 4TM. At 10°C, growth was significantly reduced at both pHs by all tested levels. At 24°C, a listeriostatic effect of Opti.Form 4TM was observed in broth containing 2.7 % at pH 6.0. These results suggest that even 1.1% Opti.Form 4TM can be used as a substantial hurdle to the growth of L. monocytogenes at low pH and temperature, but at least 1.8% of Opti.Form 4TM is needed to inhibit its growth at 24°C.
Session 29F, Food Microbiology: Control of foodborne microorganisms by antimicrobials
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