Survival and Growth of Listeria monocytogenes in Broth as a Function of Temperature, pH, and Potassium Lactate and Sodium Diacetate Concentrations

Author:

ABOU-ZEID K. A.12,YOON K. S.13,OSCAR T. P.4,SCHWARZ J. G.1,HASHEM F. M.1,WHITING R. C.5

Affiliation:

1. 1Center for Food Science and Technology, University of Maryland Eastern Shore, Princess Anne, Maryland 21853, USA

2. 2Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, New York 14853, USA

3. 3Department of Food and Nutrition, Kyung Hee University, Seoul, Republic of Korea 130-701

4. 4Microbial Food Safety Research Unit, U.S. Department of Agriculture, Agricultural Research Service, University of Maryland Eastern Shore, Princess Anne, Maryland 21853, USA

5. 5Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, 5100 Paint Branch Parkway, College Park, Maryland 20740, USA

Abstract

The objective of this study was to determine the antimicrobial effect of a combination of potassium lactate and sodium diacetate (0, 1.8, 3, and 4.5%; PURASAL P Opti.Form 4, 60% solution) on the survival and growth of Listeria monocytogenes Scott A in pH-adjusted broth (5.5, 6.0, 6.5, and 7.0) stored at 4, 10, 17, 24, 30, and 37°C. Appropriate dilutions of broth were enumerated by spiral plating on tryptose agar and counted with an automated colony counter. Growth data were iteratively fit, using nonlinear regression analysis to a three-phase linear model, using GraphPad PRISM. At pH 5.5, the combination of lactate-diacetate fully inhibited (P < 0.001) the growth of L. monocytogenes at all four levels and six temperatures. At pH 6.0, addition of 1.8% lactate-diacetate reduced (P < 0.001) the specific growth rate of L. monocytogenes and increased lag time; however, 3 and 4.5% completely inhibited the growth at the six temperatures studied. Efficacy of the lactate-diacetate mixture was decreased as pH increased and incubation temperature increased. Thus, at pH 6.5, at least 3% was required to retard (P < 0.001) the growth of L. monocytogenes in broth. There was a limited effect of the lactate-diacetate level on the specific growth rate of the pathogen at pH 7.0. However, 1.8 and 3% significantly lengthened the lag time at 4 and 10°C. These results suggest that 1.8% of lactate-diacetate mixture can be used as a substantial hurdle to the growth of L. monocytogenes when refrigerated temperatures are maintained for products with pH less than 6.5.

Publisher

International Association for Food Protection

Subject

Microbiology,Food Science

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