QUANTITATIVE ANALYSIS OF VERTICAL TRANSLOCATION AND LATERAL CROSS‐CONTAMINATION OF ESCHERICHIA COLI O157:H7 DURING MECHANICAL TENDERIZATION OF BEEF

Quantitative vertical translocation and lateral cross-contamination of Escherichia coli O157:H7 during mechanical tenderization of beef meat were investigated using a restaurant-style meat tenderizer, which was first used to tenderize a surface-inoculated sample, and then an additional four uninoculated samples. It was observed that the vertically translocated bacteria (in log10 cfu/g) was directly proportional to the logarithm of the tenderization depth, with an average translocation coefficient of 3.14 ± 0.66 log10 cfu/g per log10 mm of depth. For lateral cross-contamination, the bacterial counts recovered from the top layers of the first four pieces of meat decreased by approximately 0.5 log10 cfu/g after each tenderization. There was no decrease in the bacterial counts recovered from the top layers after the 4th tenderization. More tenderization studies were needed to quantitatively analyze the trend of lateral cross-contamination. However, it is evident that both vertical translocation and lateral cross-contamination can occur during mechanical tenderization of meat. PRACTICAL APPLICATIONS Foodborne illnesses caused by consumption of undercooked non-intact beef meats contaminated with Escherichia coli O157:H7 are an emerging public food safety concern as evidenced by a major outbreak recently. This study investigated both vertical translocation and lateral cross-contamination of E. coli O157:H7 during mechanical tenderization of beef. The results from this work can aid quantitative assessment of risks caused by non-intact beef meats.