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Title: DISTRIBUTION PATTERNS OF ESCHERICHIA COLI O157:H7 IN GROUND BEEF PRODUCED BY A LABORATORY-SCALE GRINDER.

Author
item Flores, Rolando
item Tamplin, Mark

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2002
Publication Date: 12/15/2002
Citation: Flores, R.A., Tamplin, M.L. 2002. Distribution patterns of escherichia coli o157:h7 in ground beef produced by a laboratory-scale grinder.. Journal of Food Protection. v. 65. p. 1894-1902.

Interpretive Summary: Epidemiological studies show that foodborne illnesses caused by Escherichia coli O157:H7 have been associated with contaminated meat grinders. However, there is inadequate information about the effects of meat grinders on the distribution of E. coli O157:H7 in ground beef products. This study was designed to characterize the effects of a small-scale grinder on the distribution of E. coli O157:H7 in ground beef when a single contaminated beef trim was introduced into a stream of uncontaminated beef trims. Seven levels of E. coli O157:H7 were evaluated in different batches of ground beef for the presence and quantity of E. coli O157:H7. It was found that the grinder distributes E. coli O157:H7 over a larger quantity of meat compared to the original size of the individual contaminated beef trim. A linear relationship was determined between the initial contamination on the beef trim and the amount of contaminated ground beef, normally contaminating 100% (330g) of the ground beef. Also, it was found that the nut (collar) of the grinder is a reservoir of contamination. These results may be useful for designing grinders that reduce contamination and improve sanitation practices.

Technical Abstract: This research studied the distribution patterns of E. coli O157:H7 in ground beef when a contaminated beef trim was introduced into a batch of uncontaminated beef prior to grinding in a small-scale laboratory grinder. A beef trim was inoculated with a rifampicin-resistant (rif) strain of E. coli O157:H7 and introduced into a stream of non-contaminated beef prior to grinding. Seven inoculum levels were studied (6, 5, 4 [high]; and 3, 2, 1 and 0 [low] total log CFU) in triplicate. E. coli O157:H7rif was not detected in 3.1 to 43% of the total ground beef inoculated with the high levels, and in 3.4 to 96.9% of the ground beef inoculated with low levels. For all inoculum levels studied, the five ground beef fractions (7.8±0.6 g) with the highest pathogen levels accounted for 59 to 100% of the total pathogen detected. For all inoculum levels, there was a linear relationship between the quantities of ground beef containing E. coli O157:H7rif and the inoculum level. The quantity of E. coli O157:H7rif in the trims remaining in the grinder was proportional to the inoculum level and the location in the grinder. Different components of the grinder accumulated E. coli O157:H7rif, the most significant being the nut (collar) that attaches the die to the blade. The results of this study indicate that the grinding operation should be regarded as a distributor of microbial contamination in risk analyses of ground beef operations.