Microbiological Efficacy of an On-line Hide-on Carcass Washing Decontamination Treatment

Introduction: Most bacteria found on beef carcasses are likely transferred from the hide during skinning operation. To reduce the numbers of bacteria on hides, an on-line hide-on carcass wash with 1.5% NaOH has been implemented at some beef packing plants. The microbiological efficacy of the treatment, however, has not been unequivocally established.

Purpose: The objective of this study was to determine the effects of the hide-on carcass wash on the microbiological condition of carcasses.

Methods:  On each of 5 days, 5 samples were collected from each of the following areas on carcasses during processing: rump before hide-on wash (RBHW), rump after hide-on wash (RAHW), rump after skinning (RAS), brisket after skinning (BAS), and randomly selected areas at the end of the dressing process (EDP). The numbers of total aerobes and Escherichia coli were determined. A total number of 140 E. coli isolates recovered were subtyped using multiple-locus variable-tandem-repeat analysis (MLVA).

Results: The numbers of total aerobes recovered from RBHW, RAHW, RAS, BAS and EDP were 6.38, 4.88, 2.44, 1.97 and 2.53 log CFU/1000 cm², respectively. The number of E. coli recovered from RBHW was 5.12 log CFU/1000 cm². E. coli were not recovered from RAHW and BAS; and were sporadically recovered from RAS and EDP, with total numbers of 2.15 and 1.95 log CFU/25,000 cm², respectively. Substantial fractions of the E. coli populations from RAS and EDP were not found on the hide before the hide-on wash.

Significance: The findings show that the hide-on wash is effective for reducing the numbers of bacteria on carcasses, and E. coli is more susceptible to the treatment. E. coli is transferred onto carcass from hide during skinning as well as from sources other than the hide during the dressing process.