Microbiological and Visual Effects of Trimming and/or Spray Washing for Removal of Fecal Material from Beef

Microbiological and visual evaluations were performed to compare the efficacy of hand trimming, spray washing, or a combination of treatments, in the removal of bacteria and fecal material from beef adipose tissue. Subcutaneous adipose samples with intact fascia from the surfaces of briskets (obtained within 15 min postmortem) were inoculated on different sizes of surface areas (0, 0.3125, 0,625, 1.25, 1.875, or 2.50 cm²) with a bovine fecal paste containing a culture of streptomycin-resistant Escherichia coli ATCC 11370. The samples were then spray washed with water at 35°C in a specially designed automated spray washing cabinet at pressures of 2.76, 13.79, 20.68, or 27.58 bar and at chain speeds equivalent to 100, 200, or 300 carcasses per hour (exposure times of 36, 18, or 12 s). Total aerobic mesophilic plate counts, streptomycin-resistant bacterial plate counts and visual scores for fecal contamination were obtained. There was a reduction (P < 0.05) in microbiological counts on the treated samples compared with those on the unwashed and/or untrimmed inoculated (control) samples. The variation in removal of fecal material from, and in reduction of microbiological contamination on, different sizes of surface areas of fecal material contamination and with different chain-speeds was minor under the conditions of the study. Hand trimming followed by spray washing compared to spray washing alone were similiar in their effectiveness for reduction of microbiological contamination and slightly different in the extent of fecal material removal. Overall, however, higher spray washing pressures (20.68 or 27.58 bar) were more effective (P < 0.05) than the lower spray washing pressures (2.76 or 13.79 bar) in removing fecal material from and reducing bacterial numbers on adipose tissue samples.