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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL MODELING AND BIOINFORMATICS FOR FOOD SAFETY AND SECURITY

Location: Residue Chemistry and Predictive Microbiology

Title: Modeling Transfer of Listria Monocytogenes Between Meat Slicer and Ham During Slicing

Authors
item SHEEN, SHIOWSHUH
item HWANG, CHENG-AN

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 4, 2007
Publication Date: July 8, 2007
Citation: Sheen, S., Hwang, C. 2007. Modeling transfer of listria monocytogenes between meat slicer and ham during slicing. Abstract. International Association for Food Protection. T7-06.

Technical Abstract: Listeria monocytogenes has been implicated in several listeriosis outbreaks linked to the consumption of pre-sliced ready-to-eat (RTE) deli meats. The possible contamination of sliced RTE meats by L. monocytogenes during the slicing process has become a public health concern. The objectives of this study were to investigate the transfer phenomena of L. monocytogenes between a meat slicer and ham slices, and to develop empirical models to describe the transfer during slicing. A six-strain cocktail of L. monocytogenes was inoculated onto a slicer blade to an initial level of ca. 3, 6, or 9 log CFU/blade, and then the ham was sliced to a thickness of 1-2 mm (Case I). As a second (Case I) cross-contamination scenario, a clean blade was used to slice ham that was previously inoculated with L. monocytogenes (3, 6 ,or 9 log10 CFU per meat surface per test) followed by slicing of ham that was not inoculated. The ham slicing rate was maintained at an average of 3 slices per minute for both Case I and II. Although the recovery ratio was less than 100 percent, more ham slices were contaminated with L. monocytogenes when the blade was contaminated with higher rather than lower initial levels of L. monocytogenes. For Case I, the number of contaminated slices compared to the total number of ham slices collected was 5/40, 30/40 and 150/150 for inoculation levels of 3, 6, and 9 log CFU/blade, respectively. Results for Case II showed that L. monocytogenes stayed on the blade longer and contaminated more ham slices than results observed for Case I, that being 5/40, 110/120, and 150/150 for inoculation levels of 3, 6 or 9 log CFU/test, respectively. The microbial count on the 150th consecutive slice starting from an initial level of 9 log CFU level was about 1.0 log CFU higher for Case II than for Case I. The empirical models developed [F-statistic: P > F (< 0.000) and R-square > 0.7] predicted the trend of Listeria transfer between the blade and ham slices. The models may be applied to predict the number of ham slices that may be contaminated by a L. monocytogenes-contaminated slicer during ham slicing operation.

Last Modified: 9/29/2014
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