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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL MODELING AND BIOINFORMATICS FOR FOOD SAFETY AND SECURITY Title: Modeling the surface cross-contamination of Salmonella spp. on ready-to-eat meat via a slicing operation

Authors
item Sheen, Shiowshuh
item Hwang, Cheng-An

Submitted to: Food and Nutrition Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 30, 2011
Publication Date: November 7, 2011
Citation: Sheen, S., Hwang, C. 2011. Modeling the surface cross-contamination of Salmonella spp. on ready-to-eat meat via a slicing operation. Food and Nutrition Sciences. 2:916-924.

Interpretive Summary: Cross-contamination of food pathogens at the production site is one of the major sources of contamination and may lead to foodborne illness. We investigated the surface cross-contamination of Salmonella during a ham slicing operation and developed models to predict the fate of the pathogen. The surface cross-contamination persisted longer in the “contaminated-ham to blade to ham” scenario as compared to the “direct-blade inoculation to ham” case. The Salmonella transfer models were dependent on microbial load, sliced ham number, and contamination route. These are the first available models to take those parameters into account for the slicing process and will serve as a building block in microbial risk assessment to enhance food safety.

Technical Abstract: Food pathogen cross-contamination occurring in the home or at retail food service or the production site is a major factor contributing to food-borne illness. Studies on Salmonella spp. surface transfer on ready-to-eat (RTE) deli meat and the slicer used for slicing RTE products are needed to ensure RTE food safety with respect to this pathogen. The objectives of this study were to investigate and to model the surface cross-contamination of Salmonella during the slicing operation. A five-strain cocktail of Salmonella spp. was inoculated directly onto a round slicer blade rim area at an initial level of ca. 4, 5, 6, 7 or 8 log CFU/blade (ca. 3, 4, 5, 6 or 7 log CFU/cm-squared of the blade edge area). Thereafter, a RTE deli meat (ham) was sliced to a thickness of 1-2 mm. For another cross-contamination scenario, a clean blade was initially used to slice ham, which was pre-surface-inoculated with the Salmonella cocktail (ca. 2, 3, 4, 5, 6 or 7 log CFU/cm-squared with a total area of 100 cm-squared), followed by slicing an un-inoculated ham. Empirical models were developed. These models were reasonably accurate in describing the surface transfer trend/pattern of Salmonella between the blade and ham slices when the total inoculum level was greater than or equal to 5 log CFU on the ham or blade. With an initial inoculum level equal to or less than 4 log CFU, the experimental data showed a rather random microbial surface transfer mode. Overall, the developed non-linear models, which depend on microbial load and sequential slice index (operation time related), showed a highly significant F-statistic test result (i.e. P>F (< 0.0001)) and the regression coefficient (R-squared) was greater than 0.65. The models predict the surface cross-contamination of Salmonella spp. (at any initial level) for sliced deli meat (ham) and will provide a useful tool in developing the RTE meat risk assessment.

Last Modified: 10/31/2014
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