title: Thermal inactivation of Escherichia coli O157:H7 in blade-tenderized beef steaks cooked on a commercial open-flame gas grill.
abstract: Beef subprimals were inoculated on the lean side with ca. 4.0 log CFU/g of a cocktail of rifampin-resistant (Rif(r)) Escherichia coli O157:H7 strains and then passed once through a mechanical blade tenderizer with the lean side facing upward. Inoculated subprimals that were not tenderized served as controls. Two core samples were removed from each of three tenderized subprimals and cut into six consecutive segments starting from the inoculated side. A total of six cores were also obtained from control subprimals, but only segment 1 (topmost) was sampled. Levels of E. coli O157:H7 recovered from segment 1 were 3.81 log CFU/g for the control subprimals and 3.36 log CFU/g for tenderized subprimals. The percentage of cells recovered in segment 2 was ca. 25-fold lower than levels recovered from segment 1, but E. coli O157:H7 was recovered from all six segments of the cores obtained from tenderized subprimals. In phase II, lean-side-inoculated (ca. 4.0 log CFU/g), single-pass tenderized subprimals were cut into steaks of various thicknesses (1.91 cm [0.75 in.], 2.54 cm [1.0 in.], and 3.18 cm [1.25 in.]) that were subsequently cooked on a commercial open-flame gas grill to internal temperatures of 48.8 degrees C (120 degrees F), 54.4 degrees C (130 degrees F), and 60 degrees C (140 degrees F). In general, regardless of temperature or thickness, we observed about a 2.6- to 4.2-log CFU/g reduction in pathogen levels following cooking. These data validate that cooking on a commercial gas grill is effective at eliminating relatively low levels of the pathogen that may be distributed throughout a blade-tenderized steak.
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, Microbial Food Safety Research Unit, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA. John.Luchansky@ars.usda.gov
authors.forename: John B
authors.initials: JB
authors.lastname: Luchansky
authors.forename: Anna C S
authors.initials: AC
authors.lastname: Porto-Fett
authors.forename: Bradley
authors.initials: B
authors.lastname: Shoyer
authors.forename: Randall K
authors.initials: RK
authors.lastname: Phebus
authors.forename: Harshavardhan
authors.initials: H
authors.lastname: Thippareddi
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Call
mesh_terms: D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D003296:Cooking / Q000379:methods; D004866:Equipment Contamination; D019453:Escherichia coli O157 / Q000254:growth & development*; D005506:Food Contamination / Q000032:analysis*; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006358:Hot Temperature; D006801:Humans; D008460:Meat / Q000382:microbiology*