Identification of critical control points for control of microbiological contamination in processes leading to the production of ground beef at a packing plant

Abstract

Carcasses, carcass portions and pieces of manufacturing beef were sampled by swabbing a 100 cm 2 randomly selected site on each of 25 randomly selected product units at each of several stages of the meat production processes at a large beef packing plant. After skinning, aerobes were recovered from each sample, at log mean numbers of 1.86 log cfu cm −2; and coliforms and Escherichia coli were recovered from <15 of 25 samples at log total numbers of 3.27 and 3.16 log cfu 2500 cm −2. The numbers of bacteria recovered after preevisceration washing and spraying with 2% lactic acid solution were similar to the numbers recovered after skinning, and the numbers recovered from carcasses that had been eviscerated, split, vacuum/hot-water cleaned and trimmed were little different. However, the numbers of coliforms and E. coli were reduced by the washing of carcass sides; and pasteurizing followed by spraying with lactic acid reduced the numbers of aerobes to log mean numbers of 0.71 log cfu cm −2 and coliforms and E. coli to log total numbers of 1.28 and 0.30 log cfu 2500 cm −2, respectively. After cooling for 24 h, numbers of aerobes on carcass sides had increased to log mean numbers of 2.57 log cfu cm −2, and log total numbers of coliforms and E. coli had increased to 3.34 and 2.18 log cfu 2500 cm −2, respectively. Numbers had not increased after sides had been held for a further 12 h before breaking. Numbers of bacteria on forequarters increased during breaking operations on hanging sides and increased further after forequarters were dropped to conveyor belts. Numbers on hindquarters were little affected by those operations. Large numbers of bacteria were recovered from cleaned equipment that contacted forequarters. The numbers of bacteria on trimmings did not increase during conveying from breaking lines to bulk containers. The numbers of bacteria on manufacturing beef were less than the numbers on forequarters trimmings, but more than the numbers on hindquarters trimmings. The log mean numbers of bacteria in ground beef produced at the plant were 3.11 log cfu g −1, and the log total numbers of coliforms and E. coli were 1.84 and 1.30 log cfu 25 g −1, respectively. Similar numbers of bacteria were recovered from ground samples of manufacturing beef. It therefore appears that most of the E. coli as well as other bacteria in ground beef are deposited on the product during the initial operations for breaking forequarters. Thus, improvement of equipment cleaning rather than of production processes would be required to improve the microbiological condition of ground beef prepared at the plant. However, skinning, washing of dressed sides, pasteurizing and cooling are evidently critical control points in carcass production processes.