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The objective of this study was to evaluate the thermal inactivation of Escherichia coliO157:H7 in ground beef cooked to an internal temperature of 71.1°C (160°F) under conditions simulating consumer-style cooking methods. To compare a double-sided grill (DSG) with a single-sided grill (SSG), two different cooking methods were used for the SSG: for the one-turnover (OT-SSG) method, a patty was turned once when the internal temperature reached 40°C, and for the multiturnover (MT-SSG) method, a patty was turned every 30 s. Patties (100 g, n= 9) inoculated with a five-strain mixture of E. coliO157: H7 at a concentration of 107CFU/g were cooked until all three temperature readings (for two sides and the center) for a patty were 71.1°C. The surviving E. coliO157:H7 cells were enumerated on sorbitol MacConkey (SMAC) agar and on phenol red agar base with 1% sorbitol (SPRAB). The order of the cooking methods with regard to the cooking time required for the patty to reach 71.1°C was as follows: DSG (2.7 min) < MT-SSG (6.6 min) < OT-SSG (10.9 min). The more rapid, higher-temperature cooking method was more effective (P< 0.01) in destroying E. coliO157:H7 in ground beef. E. coliO157:H7 reduction levels were clearly differentiated among treatments as follows: OT-SSG (4.7 log10CFU/g) < MT-SSG (5.6 log10CFU/g) < DSG (6.9 log10CFU/g). Significantly larger numbers of E. coliO157:H7 were observed on SPRAB than on SMAC agar. To confirm the safety of ground beef cooked to 71.1°C, additional patties (100 g, n= 9) inoculated with lower concentrations of E. coliO157:H7 (103to 104CFU/g) were tested. The ground beef cooked by the OT-SSG method resulted in two (22%) of nine samples testing positive after enrichment, whereas no E. coliO157:H7 was found for samples cooked by the MT-SSG and DSG methods. Our findings suggest that consumers should be advised to either cook ground beef patties in a grill that cooks the top and the bottom of the patty at the same time or turn patties frequently (every 30 s) when cooking on a grill that cooks on only one side.

Reports on a national panel of food experts' identification of consumer food-handling concepts that would protect against foodborne illnesses, if practiced. Use of the concepts as the basis for food safety curricula; Pilot-testing of knowledge and attitude questions with a variety of consumer groups; Conduction of reliability and validity tests.