Effect of water temperature, pressure and chemical solution on removal of fecal material and bacteria from lamb adipose tissue by spray-washing

Abstract

The objectives of this study were to determine the efficacy of various water temperatures, pressures and chemical solutions of spray-washing on the removal of fecal and bacterial contamination from lamb carcass samples taken from the breast area (< 15 min post mortem) and inoculated (6.50 cm 2 area) with an ovine fecal paste containing Escherichia coli (ATCC 11370). Inoculated samples were held for 15 min and then knife-trimmed and/or spraywashed with varying water temperatures (16, 35 or 74 °C), pressures (2.76, 13.79, 20.68 or 27.58 bar) and chemical solutions (12% trisodium phosphate, 2% acetic acid, 5% hydrogen peroxide or 0.003% available chlorine) for 18 s. After the respective treatments, samples were evaluated visually for presence of fecal material and microbiologically for aerobic plate counts (APC). Knife-trimming reduced ( p < 0.05) APC of inoculated samples, while subsequent spray-washing of knife-trimmed samples reduced APC ( p < 0.05), even compared to uninoculated control samples. Spray-washing with any temperature and pressure combination reduced ( p < 0.05) visible fecal contamination on the samples. Bacterial reductions ranged from 1.48 to 3.83 log colony forming units (CFU/cm 2) at the inoculation site. Use of 74 °C water was more effective ( p < 0.05) in decreasing APC than either 16 or 35 °C water, while water pressure effects were similar. Use of 2% acetic acid reduced the APC more than the use of any other chemical solution tested. APC for the areas surrounding the inoculation site were similar to APC at the inoculation site; thus indicating that either there was no major spread of bacterial contamination to areas above or below the inoculation site or that contamination was diluted to levels lower than initial contamination. Overall, acetic acid and water temperature were the most important factors in reducing APC and fecal contamination on lamb adipose tissue.