Validation of time and temperature values as critical limits for the control of Escherichia coli O157:H7 during the production of fresh ground beef

In order to provide beef processors with valuable data to validate critical limits set for temperature during grinding, a study was conducted to determine Escherichia coli O157:H7 growth at various temperatures in raw ground beef. Fresh ground beef samples were inoculated with a cocktail mixture of streptomycin-resistant E coli O157:H7 to facilitate recovery in the presence of background flora. Samples were held at 4.4, 7.2, and 10 degrees C, and at room temperature (22.2 to 23.3 degrees C) to mimic typical processing and holding temperatures observed in meat processing environments. E. coli O157:H7 counts were determined by direct plating Onto tryptic soy agar with streptomycin (1,000 mu g/ml), at 2-h intervals over 12 h for samples held at room temperature. Samples held under refrigeration temperatures were sampled at 4, 8, 12, 24, 48, and 72 h. Less than one log of E. coli O157:H7 growth was observed at 48 h for samples held at 10 degrees C. Samples held at 4.4 and 7.2 degrees C showed less than one log of E. coli O157:H7 growth at 72 It. Samples held at room temperature showed no significant increase in E. coli O157:H7 counts for the first 6 h, but increased significantly afterwards. These results illustrate that meat processors can utilize a variety of time and temperature combinations as critical limits in their hazard analysis critical control point plans to minimize E. coli O157:H7 growth during the production and storage of ground beef.