Process Mapping the Prevalence of Salmonella Contamination on Pork Carcass from Slaughter to Chilling

Current processing procedures generally lead to a lowering in the prevalence of Salmonella as the carcasses move towards the cooler, according to researchers in the US who reviewed 44 studies evaluating pork carcass contamination levels at various stages of processing in plants in several countries.
calendar icon 10 May 2012
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A systematic review was conducted by Annette M. O’Connor of Iowa State University and others there and at the University of Maryland and Pennsylvania State University to identify and summarise primary research studies that describe the prevalence of Salmonella species in pork from slaughter to cooler in the member states of the European Union (EU), Australia, Canada, Hong Kong, Japan, Korea, Mexico, New Zealand, Taiwan and United States, i.e. a process map. Their paper is published in the journal, Foodborne Pathogens and Disease.

Relevant studies documented Salmonella spp. prevalence at more than one processing point using the same cohort of pigs or the same production line for the post-cooler component. Literature searches retrieved 6,811 citations. Sixteen publications, describing 44 studies, evaluated the presence of Salmonella on pork carcasses.

The carcass sampling points evaluated were as follows: stun, bleed, kill, scald, dehair, singe, polish, bung removal, evisceration, split, stamp, final wash, immediately after chill, and 18 to 48 hours after chilling. Seventy-eight comparisons of Salmonella prevalence between points along the processing line were reported.

The median prevalence of Salmonella–positive carcasses evaluated in the cooler was zero. The median prevalence of Salmonella after bleeding was 32 per cent. Fifty-nine of the 78 point-to-point comparisons were associated with either no change or a decrease in Salmonella prevalence as the carcass moved closer to the cooler.

Nineteen point-to-point changes showed an increase in Salmonella prevalence as the carcass moved toward the cooler; of these, six reported a greater than 10 per cent increase in Salmonella prevalence. The majority of increases were associated with post-evisceration and splitting.

These findings suggest that the processing procedures in place generally result in decreased prevalence of Salmonella as the carcasses move toward the cooler, concluded O’Connor and her co-authors.


O’Connor A.M., B. Wang, T. Denagamage and J. McKean. 2012. Process mapping the prevalence of Salmonella contamination on pork carcass from slaughter to chilling: a systematic review approach. Foodborne Pathogens and Disease. 9(5):386-395. doi:10.1089/fpd.2011.1040

Further Reading

- You can view the full report by clicking here.

May 2012
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