Transfer of Listera monocytogenes and Escherichia coli 0157:H7 during food processing

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] In the study of the transfer of L. monocytogenes from an inoculated slicer to roast beef products, at the high inoculum level of 108 CFU/ml, cells transferred per slice decreased logarithmically with a 2 log CFU/g decrease after 40 slices. The cell count from each documented slice significantly differed from each other (P [less than or equal to] 0.05). A linear-logarithmic trend was observed (R2 = 0.93) for transfer cell counts obtained at a high inoculum level. In the study of transfer of GFP-marked E. coli O157:H7 from an inoculated meat grinder to raw beef products at the high inoculum level of 109 CFU/ml, the number of E. coli O157:H7 recovered from beef samples decreased logarithmically to 103 CFU/g after a total of 7.5 kg beef was ground (R2 =0.90). E. coli O157:H7 in the ground beef decreased significantly (P [lesser than or equal to] 0.05). In both studies, at the low inoculum level of 103 CFU/ml, L. monocytogenes and E. coli O157:H7 recovered could not be accurately quantified by a direct plating count. Analysis by enrichment indicated the prolonged persistence of these pathogens, which indicated these pathogens will be very hard to remove one established. Our studies demonstrated the importance of cleaning and sanitizing of beef processing equipment and confirmed the importance of disassembling, cleaning and sanitizing of equipment before, during and after processing.--From short.pdf