Reduction of Bacteria on Pork Carcasses Associated with Chilling Method

Abstract

In addition to reducing the temperature of pork carcasses immediately after slaughter and before fabrication, blast chilling (snap chill) or conventional chilling can reduce bacterial populations associated with fresh meats. However, there is little information on bacteria survival resulting from the freeze or chill injury of meat products. In this study, porcine fecal slurries with and without pathogens (Listeria monocytogenes, Salmonella Typhimurium, and Campylobacter coli) were inoculated onto skin-on and skin-off pork surfaces and subjected to industry-specific blast or conventional chilling conditions. A thin agar layer method was used for the recovery of freeze- or chill-injured cells. Test results indicated that there were no statistically significant (P > 0.05) differences between blast and conventional chilling treatments with respect to the reduction of high and low inoculation levels of mesophilic aerobic bacteria, total coliforms, or Escherichia coli on either skin-on or skin-off surfaces. Chilling treatments did not differ significantly (P > 0.05) with respect to their ability to reduce low (3 log10 CFU/cm2) levels of L. monocytogenes and Salmonella Typhimurium. However, C. coli was reduced to undetectable levels, even after enrichment, on pork surfaces inoculated with low levels (3 log10 CFU/cm2) and subjected to blast chilling. Blast and conventional chilling treatments were more effective against all pathogenic bacterial populations when pork surfaces where inoculated at high levels (5 log10 CFU/cm2). The effects of chilling techniques on microbial populations could provide pork processors with an additional intervention for pork slaughter or information to modify and/or improve the chilling process. The information obtained from this study has the potential to serve as a means of producing a microbiologically safer product.