Microbiological attributes of freeze-chilled pork carcasses

Abstract

A combination of freeze chilling and normal chiUing of pork carcasses was compared to normal chiUing at conventional chilling temperatures with regard to carcass surface microbial load, temperature and pH decline. Fifty pork carcasses from a commercial facility were assigned to five treatment groups (i.e. normal chiU (NC) at 2°C for 24 hr. and freeze chiU for 60, 90, 120, and 150 min. in combination with normal chiUing for a total of 24 hr chilling duration. Temperature and pH measurements were taken on loin and ham at 0, 1, 2, 3, 4, 5 and 24 hours chiQing time. Core samples were analyzed for aerobic plate count (APC), lactic acid bacteria (LAB), S. aureus, Salmonella spp. coliforms and Escherichia coli.

No Salmonella spp. was detected in all the samples analyzed. E. coli. and coliform counts were very low (< 0.6 log CFU/g). There was significant (P < 0.05) drop in S. aureus estimates only when carcasses were freeze chilled for 150 minutes. Freeze chilling for 90, 120, and 150 minutes significantly reduced the APC counts (P < 0.05). These results indicate that the microflora of chÍQed meat carcasses is mainly composed of lactic acid bacteria. Freeze chilling can be used to decrease the microbial population in pork, however the magnitude of the effect depends mainly on the type of bacteria initially prevalent on the carcass.