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.

High Stability of Stx2 Phage in Food and under Food-Processing Conditions

“…2). It is recommended that hamburgers reach an internal temperature of 71.1°C (26), but undercooked hamburgers are a frequent cause of EHEC infections (18). We found that at 60°C, the matrix seemed to have an effect on the inactivity.…”

“…Thermal inactivation is regarded as a central postprocessing method for reducing the level of STEC in food, and several food-borne outbreaks are due to undercooked beef or ground beef (12,26). As expected, heating also reduced the infectivity of the phages, and the reduction was faster at the highest temperature (Fig.…”

Using UVC Light-Emitting Diodes at Wavelengths of 266 to 279 Nanometers To Inactivate Foodborne Pathogens and Pasteurize Sliced Cheese

“…Enumeration of injured E. coli O157:H7 was accomplished with phenol red agar base with 1% sorbitol (SPRAB) (14). After 37°C, 24 h of incubation, typical white colonies were enumerated and, simultaneously, serological confirmation using a RIM E. coli O157:H7 latex agglutination test (Remel, Lenexa, KS) was performed on randomly selected presumptive colonies of E. coli O157:H7.…”

Simultaneous Near-Infrared Radiant Heating and UV Radiation for Inactivating Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in Powdered Red Pepper (Capsicum annuum L.)

“…Following incubation, presumptive colonies of S. Typhimurium with typical black colonies were enumerated. For enumerating injured cells of E. coli O157:H7, phenol red agar base with 1% sorbitol (SPRAB; Difco) was used (24). After incubation at 37°C for 24 h, typical white colonies characteristic of E. coli O157:H7 were enumerated.…”