Survivability of E. coli O157:H7 in needle tenderized beef steaks during lactic acid application and cooking

Illness has been associated with the consumption of non-intact beef products. Because blade tenderization is commonly used in the beef industry to improve meat tenderness, measures must be taken to reduce the threat the pathogen translocation from the surface of beef cuts during mechanical tenderization. The objective of this research was to characterize the effects of 5% lactic acid on needle-tenderized beef strip loins inoculated with Escherichia coli O157:H7 and managed under simulated industry conditions prior to cooking to various endpoint temperatures. Subprimals were inoculated with either a low or high level of E. coli O157:H7 (103CFU/cm2 and 105CFU/cm2, respectively) using a dip method at the BSL-II pathogen processing facility, at Texas Tech University (Lubbock, TX). Subprimals were then stored for 7 days at 2-4oC. At 7 days, subprimals were mechanically tenderized (Model H, Jaccard, Orchard Park, NY) and cut into 2.54 cm2 thick steaks, then stored at 2-40C for 21 days. At 28 days, the steaks were transported to the Experimental Sciences Building (ESB), at Texas Tech University (Lubbock, TX) to be cooked to internal temperatures of 55, 60, 65, 70, or 75oC. At low inoculation levels (103cfu/cm2), after processing, and cooking, E. coli O157:H7 was not detected on internal meat samples. However, E. coli was detected when high inoculums steaks (105cfu/cm2) that were cooked to 55, 60, or 70⁰C. Regardless, at low inoculation levels (typical of industry contamination) 5% lactic acid treatment, vacuum packaging, refrigerated storage and cooking reduced E. coli O157:H7 to non-detectable levels in needle tenderized beef steaks cooked to 55°C or higher internal temperatures.