Survivability of Escherichia coli O157:H7 in mechanically tenderized beef steaks subjected to lactic acid application and cooking under simulated industry conditions

Mechanical tenderization improves the palatability of beef; however, it increases the risk of translocating pathogenic bacteria to the interior of beef cuts. This study investigated the efficacies of lactic acid spray (LA; 5%), storage, and cooking on the survivability of Escherichia coli O157:H7 in mechanically tenderized beef steaks managed under simulated industry conditions. Beef subprimals inoculated with either high (10⁵ CFU/ml) or low (10³ CFU/ml) levels of E. coli O157:H7 were treated (LA or control) and stored for 21 days prior to mechanical tenderization, steak portioning (2.54 cm), and additional storage for 7 days. Steaks were then cooked to an internal temperature of 55, 60, 65, 70, or 75°C. Samples were enumerated and analyzed using DNA-based methods. Treatment with LA immediately reduced E. coli O157:H7 on the lean and fat surfaces of high- and lowinoculum- treated subprimals by more than 1.0 log CFU/cm² (P < 0.05). Storage for 21 days reduced surface populations of E. coli O157:H7 regardless of the inoculation level; however, the populations on LA- and control-treated lean surfaces of high- and low-inoculum-treated subprimals were not different after 21 days (P > 0.05). E. coli O157:H7 was detected in core samples from high-inoculum-treated steaks cooked to 55, 60, or 70°C. Conversely, E. coli O157:H7 was not detected in core samples from low-inoculum-treated steaks, regardless of the internal cooking temperature. These data suggest that LA- and storage-mediated reduction of pathogens on subprimals exposed to typical industry contamination levels (10¹ CFU/cm²) reduces the risk of pathogen translocation and subsequent survival after cooking.