Fate of Shiga Toxin–Producing O157:H7 and Non-O157:H7 Escherichia coli Cells within Refrigerated, Frozen, or Frozen Then Thawed Ground Beef Patties Cooked on a Commercial Open-Flame Gas or a Clamshell Electric Grill

• Published in: Journal of food protection Vol. 76; no. 9; pp. 1500 - 1512
• Main Authors: Luchansky, John B, Porto-Fett, Anna C.S, Shoyer, Bradley A, Phillips, John, Chen, Vivian, Eblen, Denise R, Cook, L. Victor, Mohr, Tim B, Esteban, Emilio, Bauer, Nathan
• Format: Journal Article
• Language: English
• Published: Des Moines, IA International Association for Food Protection 01.09.2013; Elsevier Limited
• Subjects: Animals; Beef; Biological and medical sciences; Cattle; Colony Count, Microbial; Consumers; Consumption; Cooking; Cooking - methods; Disease control; E coli; Escherichia coli; Escherichia coli O157; Escherichia coli O157 - growth & development; Food contamination & poisoning; Food Handling - methods; Food industries; Food irradiation; Food Microbiology; Food safety; Frozen foods; Fundamental and applied biological sciences. Psychology; Grills; ground beef; Illnesses; Infections; internal temperature; Meat Products - microbiology; Pathogens; patties; Refrigeration; Shiga Toxin - metabolism; Shiga-Toxigenic Escherichia coli - growth & development; Temperature; Toxins; Escherichia coli; Meat product; Bacteria; Frozen product; Beef; Refrigeration; Cell; Shiga like toxin; Minced meat; Enterobacteriaceae
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X.JFP-12-432

Both high-fat and low-fat ground beef (percent lean:fat = ca. 70:30 and 93:7, respectively) were inoculated with a 6-strain cocktail of non-O157:H7 Shiga toxin-producing Escherichia coli (STEC) or a five-strain cocktail of E. coli O157:H7 (ca. 7.0 log CFU/g). Patties were pressed (ca. 2.54 cm thick, ca. 300 g each) and then refrigerated (4°C, 18 to 24 h), or frozen (-18°C, 3 weeks), or frozen (-18°C, 3 weeks) and then thawed (4°C for 18 h or 21°C for 10 h) before being cooked on commercial gas or electric grills to internal temperatures of 60 to 76.6°C. For E. coli O157:H7, regardless of grill type or fat level, cooking refrigerated patties to 71.1 or 76.6°C decreased E. coli O157:H7 numbers from an initial level of ca. 7.0 log CFU/g to a final level of ≤1.0 log CFU/g, whereas decreases to ca. 1.1 to 3.1 log CFU/g were observed when refrigerated patties were cooked to 60.0 or 65.5°C. For patties that were frozen or freeze-thawed and cooked to 71.1 or 76.6°C, E. coli O157:H7 numbers decreased to ca. 1.7 or ≤0.7 log CFU/g. Likewise, pathogen numbers decreased to ca. 0.7 to 3.7 log CFU/g in patties that were frozen or freeze-thawed and cooked to 60.0 or 65.5°C. For STEC, regardless of grill type or fat level, cooking refrigerated patties to 71.1 or 76.6°C decreased pathogen numbers from ca. 7.0 to ≤0.7 log CFU/g, whereas decreases to ca. 0.7 to 3.6 log CFU/g were observed when refrigerated patties were cooked to 60.0 or 65.5°C. For patties that were frozen or freeze-thawed and cooked to 71.1 or 76.6°C, STEC numbers decreased to a final level of ca. 1.5 to ≤0.7 log CFU/g. Likewise, pathogen numbers decreased from ca. 7.0 to ca. 0.8 to 4.3 log CFU/g in patties that were frozen or freeze-thawed and cooked to 60.0 or 65.5°C. Thus, cooking ground beef patties that were refrigerated, frozen, or freeze-thawed to internal temperatures of 71.1 and 76.6°C was effective for eliminating ca. 5.1 to 7.0 log CFU of E. coli O157:H7 and STEC per g.