title: Evaluation of consumer-style cooking methods for reduction of Escherichia coli O157:H7 in ground beef.
abstract: The objective of this study was to evaluate the thermal inactivation of Escherichia coli O157:H7 in ground beef cooked to an internal temperature of 71.1 degrees C (160 degrees 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 degrees 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. coli O157: H7 at a concentration of 10(7) CFU/g were cooked until all three temperature readings (for two sides and the center) for a patty were 71.1 degrees C. The surviving E. coli O157: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 degrees 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. coli O157:H7 in ground beef. E. coli O157:H7 reduction levels were clearly differentiated among treatments as follows: OT-SSG (4.7 log10 CFU/g) < MT-SSG (5.6 log10 CFU/g) < DSG (6.9 log10 CFU/g). Significantly larger numbers of E. coil O157:H7 were observed on SPRAB than on SMAC agar. To confirm the safety of ground beef cooked to 71.1 degrees C, additional patties (100 g, n = 9) inoculated with lower concentrations of E. coli O157:H7 (10(3) to 10(4) CFU/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. coli O157: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.
authors.affiliation: Department of Food Science and Human Nutrition, Washington State University, Pullman, Washington 99164-6376, USA.
authors.forename: Min-Suk
authors.initials: MS
authors.lastname: Rhee
authors.forename: Sun-Young
authors.initials: SY
authors.lastname: Lee
authors.forename: Virginia N
authors.initials: VN
authors.lastname: Hillers
authors.forename: Sandra M
authors.initials: SM
authors.lastname: McCurdy
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Kang
mesh_terms: D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D003296:Cooking / Q000379:methods*; D003470:Culture Media; D019453:Escherichia coli O157 / Q000254:growth & development*; D005516:Food Microbiology; D006358:Hot Temperature; D006801:Humans; D008461:Meat Products / Q000382:microbiology*; D013997:Time Factors
chemical_list: D003470:Culture Media