Twenty-four dairy cows were slaughtered under commercial conditions, muscles were excised from one side within 3 h of slaughter and from the second side after 24 h chill at 3°C. Surface aerobic bacterial plate counts, (APC5, 20, and 35°C, that is, plates were incubated at 5, 20 and 35°C, respectively) obtained from the rounds immediately before deboning did not vary significantly between the hot and chilled carcasses. The APC (5, 20, and 35°C) increased (P<.01) during removal of rounds from both hot and chilled carcasses, and the magnitude of the increase was greater than one logarithm. The bacterial count on loins and rounds that were overwrapped and frozen generally was lower than on loins and rounds held at 3°C for 7 and 14 d before being frozen. The APC (5, 20, and 35°C) of fresh ground beef fabricated in 450-kg batches from trimmings of hot cow carcasses were not significantly different from that made from the chilled carcasses. Addition of chilled USDA Choice plates to increase the fat content and lower the temperature of the manufactured ground beef increased (P<.01) APC counts in most instances. The log count of the USDA Choice plates was about 5 to 6/cm2; whereas that of the cow beef was about 2 to 4/cm2. The mean counts of coliforms, fecal coliforms and Escherichia coli were usually less than one log, so significant treatment differences, when they did occur, were unimportant. Results of this research indicate that hot boning does not adversely affect the microbial quality of selected primals and ground beef.
1Presently with the Microbiology Division, Food Safety and Inspection Service, USDA, Building 322, BARC-East, Beltsville, MD 20705.