Industry-level changes in microbial contamination on market hog and broiler chicken carcasses between two locations in the slaughter process

Abstract

Pork and poultry products have been implicated in a substantial proportion of microbial foodborne illnesses such as salmonellosis and campylobacteriosis. Understanding the similarities and differences between the effectiveness of interventions applied during slaughter to the two commodities can help identify opportunities to reduce the risk of foodborne illness. This study uses data from two national surveys and censored data techniques to assess the concentrations of microbial contamination on broiler chickens and market hogs at two points in the slaughter process. Statistical distributions are fitted to estimate the average concentrations of microbial contamination, the variability in these concentrations, and the average reduction in contamination between the two locations for pork and chicken produced in the United States. The concentrations of Salmonella and generic Escherichia coli (GEC) are estimated for hog carcasses; the concentrations of Salmonella, GEC, and Campylobacter are estimated for chicken carcasses. These datasets are also used to study the magnitude of seasonal changes in concentrations of microbial contamination and to demonstrate the potential utility of using the reduction in the average aerobic plate count between the pre-evisceration and post-chill stages of the slaughter process as an indicator of the corresponding reduction in other species of bacteria. The study finds interventions for hog carcasses achieve much larger reductions in contamination than those applied to chicken. However, the variability in the concentration of Salmonella contamination on pork is significantly higher, suggesting an opportunity to decrease risk by ensuring more consistent reductions across the industry. The study also finds, for both commodities, that the log10 reductions in the concentrations of GEC are similar to the log10 reductions in Salmonella, while the log reduction in Campylobacter on chicken was substantially greater than for both GEC and Salmonella. Additional analyses demonstrate modest seasonal increases in contamination only on hog carcasses as well as demonstrating that reductions in APC are indicative of reductions in all other organisms, suggesting its potential as an effective indicator organism.