Effect of frozen storage, different thawing methods and cooking processes on the survival of Salmonella spp. and Escherichia coli O157:H7 in commercially shaped beef patties

The effect of common handling practices (i.e., freezing, thawing and cooking) of beef patties on the survival of Salmonella spp. and Escherichia coli O157:H7, was evaluated. Inoculated ground beef was stored at –22 °C for 5 and 75 days. After thawing at 4 °C/16 h, 20 °C/12 h, in microwave/22–24 min, or without prior thawing, beef patties (90 g) were shaped and cooked in oven-broiler or in pan-grill to internal temperatures of 60 °C or 71 °C. Cooking in oven-broiler was more effective compared to pan-grill, especially when cooked to 71 °C. Defrosting methods did not affect significantly (P ≥ 0.05) the survival of the pathogens during subsequent cooking. Frozen storage for 75 days enhanced the survival of E. coli O157:H7, as the pathogen survived 3.1 logCFU/g when cooked in oven-broiler at 71 °C. Results may supplement the existing guidelines for the appropriate practices, associated with freezing, thawing and cooking of patties in households or catering services.