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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL MODELING AND BIOINFORMATICS FOR FOOD SAFETY AND SECURITY Title: Effect of a native microflora on the growth of Listeria monocytogenes in cooked ham

Authors
item Hwang, Cheng-An
item Sheen, Shiowshuh

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 2010
Publication Date: August 1, 2010
Citation: Hwang, C., Sheen, S. 2010. Effect of a native microflora on the growth of Listeria monocytogenes in cooked ham [abstract]. IAFP Annual Meeting. p. 1.

Technical Abstract: Refrigerated ready-to-eat meat products contaminated with Listeria monocytogenes have been linked to outbreaks of foodborne illnesses. L. monocytogenes contamination was mainly caused by improper processing and/or cross-contamination. This study examined the growth characteristics of L. monocytogenes as affected by native microflora in cooked ham at refrigerated and abuse temperatures. A five-strain mixture of L. monocytogenes was onto cooked ham slices inoculated alone (monocultured) or co-inoculated (co-cultured) with a native microflora, consisting of Brochothrix spp. isolated from ham products. Ham slices were vacuum-packed and stored at 4, 6, 8, 10, and 12 degrees Centigrade. The growth characteristics, lag phase duration (LPD, h), growth rate (GR, log cfu/h), and maximum population density (MPD, log cfu/g), of L. monocytogenes and the native microflora during storage were determined. At 4-12 degrees Centigrade, the LPDs of co-cultured L. monocytogenes (62-32 h) were not significantly different (p>0.05) from those of monocultured L. monocytogenes (58-38 h) in ham, indicating the LPDs of L. monocytogenes were not influenced by the presence of the native microflora. At 4-8 degrees Centigrade, the GRs of co-cultured L. monocytogenes (0.0114-0.0130 log cfu/h) were significantly lower (p<0.05) than those of monocultured L. monocytogenes (0.0132-0.0145 log cfu/h), indicating the GRs of L. monocytogenes at 4-8 degrees Centigrade were reduced by the presence of the native microflora. The GR-suppression effect was not observed in ham stored at 10 and 12 degrees Centigrade. The MPDs of L. monocytogenes at 4-8 degrees Centigrade were also reduced by the native microflora. Findings from this study add to our understanding of the survival and growth of L. monocytogenes in RTE meats and can be used to design processing and handling conditions to reduce the hazards associated L. monocytogenes in these products.

Last Modified: 11/24/2014
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