The effect of blast chilling on occurrence of human pathogenic Yersinia enterocolitica compared to Campylobacter spp. and numbers of hygienic indicators on pig carcasses.

In this study, the occurrence of Yersinia enterocolitica on pig carcasses was compared to the occurrence of Campylobacter spp., and to the numbers of aerobic micro-organisms, coliform bacteria, thermotolerant coliform bacteria, and Escherichia coli before and after blast chilling. Y. enterocolitica O:3/biovar 4 was isolated from five (8.3%) of 60 carcasses before blast chilling, and also from five of them 1 h after blast chilling. Therefore this procedure does not seem to have a significant effect on the occurrence of pathogenic Y. enterocolitica on pig carcasses. Y. enterocolitica O:9/biovar 2 was isolated from a pig source in Norway for the first time when this sero/biovariant was isolated from one of the carcasses before blast chilling. Campylobacter spp. was isolated from 34 (56.7%) of 60 carcass samples before blast chilling. After blast chilling Campylobacter spp. was isolated from only one (1.7%) of the 60 carcasses. There was a significant decrease of the numbers of coliform bacteria, thermotolerant coliform bacteria and E. coli after blast chilling. The number of aerobic micro-organisms did not decrease after this step. In contrast to the drastic decrease in the occurrence of campylobacter-positive carcasses and the significant decrease of the numbers of coliform bacteria, thermotolerant coliform bacteria and E. coli, blast chilling does not seem to have a significant effect on the occurrence of human pathogenic Y. enterocolitica on pig carcasses.