Comparison of Methods for Decontamination from Beef Carcass Surfaces

Methods for the removal of fecal contamination from beef carcass surfaces were evaluated using a fecal suspension containing a rifampicin-resistant strain of either Escherichia coli O157:H7 or Salmonella typhimurium . Paired cuts from four distinct beef carcass regions (inside round, outside round, brisket, and clod) were removed from hot carcasses after splitting, and subcutaneous fat and lean carcass surfaces from these cuts were used to model decontamination of prechilled carcass surface regions. Hot carcass surface regions were contaminated with an inoculated fecal suspension in a 400-cm² area and then treated by one of four treatments either immediately or 20 to 30 min after contamination. One paired contaminated surface region from each carcass side was trimmed of all visible fecal contamination. The remaining paired carcass surface region was washed either with water (35°C) or with water followed by a 2% lactic or acetic acid spray (55°C). Surface samples were obtained for microbiological examination before and after treatment from within and outside the defined area contaminated with the fecal suspension. All treatments significantly reduced levels of pathogens; however, decontamination was significantly affected by carcass surface region. The inside round region was the most difficult carcass surface to decontaminate, regardless of treatment. Washing followed by organic acid treatment performed better than trimming or washing alone on all carcass region surfaces except the inside round, where organic acid treatments and trimming performed equally well. Overall, lactic acid reduced levels of E. coli O157:H7 significantly better than acetic acid; however, differences between the abilities of the acids to reduce Salmonella were less pronounced. All treatments caused minimal spread of pathogens outside the initial area of fecal contamination, and recovery after spreading was reduced by organic acid treatments.