ARS | Publication request: Fate of Escherichia coli O157:H7 in mechanically tenderized beef prime rib following searing, cooking and holding under commercial conditions

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 28, 2012
Publication Date: N/A

Interpretive Summary: We evaluated the effect of searing, cooking, and holding mechanically tenderized prime rib for the thermal destruction of the human pathogen Escherichia coli O157:H7. Approximately 1,000,000 cells of this pathogen were added to the surface of boneless beef ribeye (18 to 20 lbs each) and then passed once through a mechanical tenderizer. Next, the tenderized prime rib was seared and then cooked in a convection oven to a doneness ranging from rare to well. Our results confirmed that due to mechanical tenderization, cells of E. coli O157:H7 were transferred from the surface into the deeper tissues of the meat. Our results demonstrated that it would be necessary to sear, cook prime rib to a degree of doneness of medium to well, and then hold the roasts in a warming oven for up to 8 hours to reduce E. coli O157:H7 levels by 10,000 to 100,000 cells throughout the prime rib roasts.

Technical Abstract: We evaluated the effect of commercial times/temperatures for searing, cooking, and holding for the destruction of Escherichia coli O157:H7 (ECOH) from mechanically tenderized prime rib. Boneless beef ribeye was inoculated on the fat side with ca. 5.7 log CFU/g of a five-strain cocktail of ECOH and then passed once through a mechanical tenderizer with the fat side facing upwards. The inoculated and tenderized prime rib was seared at 276.7 deg C for 30 min in a conventional oven, and then cooked in a commercial convection oven at 121.1 deg C to internal temperatures of 37.8 deg C, 48.9 deg C, 60.0 deg C, and 71.1 deg C before being placed in a commercial holding oven maintained at 60.0 deg C for up to eight hours. After searing, ECOH numbers decreased by ca. 1.0 log CFU/g. Following cooking to internal temperatures of 37.8 to 71.1 deg C, pathogen numbers decreased by an additional ca. 2.7 to 4.0 log CFU/g. After cooking to 37.8 deg C, 48.9 deg C, or 60.0 deg C and then warm holding at 60.0 deg C for 2 h, pathogen numbers increased by ca. 0.2 to 0.7 log CFU/g. However, for prime rib cooked to 37.8 deg C, pathogen numbers remained relatively unchanged over the next 6 h of warm holding, whereas for those cooked to 48.9 deg C or 60.0 deg C pathogen numbers decreased by ca. 0.3 to 0.7 log CFU/g over the next 6 h of warm holding. In contrast, after cooking prime rib to 71.1 deg C and holding for up to 8 h at 60.0 deg C, ECOH numbers decreased by an additional ca. 0.5 log CFU/g. Our results demonstrated that to meet a 5.0-log reduction of ECOH, it would be necessary to sear, cook prime rib to internal temperatures of 48.9 deg C, 60.0 deg C, or 71.1 deg C, and then holding the prime rib roasts at 60.0 deg C for at least 8 h.