Microbiological and Visible Contamination of Lamb Carcasses According to Preslaughter Presentation Status: Implications for HACCP

Abstract

The effective design and implementation of hazard analysis and critical control point (HACCP) systems for fresh meat is dependent on identification of those process steps that determine most of the contamination on the carcass, and institution of appropriate critical limits. Eight groups of 25 lamb carcasses of different preslaughter presentation statuses were subjected to excision sampling at multiple sites for microbiological contamination, and detailed examination for visible contamination. Examinations were conducted in a traditional dressing system after pelting, after pre-evisceration washing, at chiller loading, and at the end of the chill cycle. Mean levels of microbiological contamination on carcasses immediately after pelting (log10 aerobic plate count/cm2) (APC) ranged from 4.63 on those derived from dirty woolly washed lambs to 3.93 on those derived from clean shorn unwashed lambs. Higher APCs were found on carcasses derived from groups of lambs with a long wool and/or dirty, and washed preslaughter status. There was a significant interaction between long wool and preslaughter washing at pelting, and differences between groups were “smoothed” as APCs generally trended downwards throughout subsequent process steps. Only long wool and preslaughter washing remained as significant factors associated with higher levels of contamination at the end of the chill cycle. Levels of visible contamination in different categories had a variable pattern, and carcasses derived from unwashed lambs had markedly higher rates of “other” and faecal contamination, a trend contrary to that for microbiological contamination. The pre-evisceration wash removed almost all contamination with wool, but had little effect on visible fecal contamination. The results of this study suggest that attempts to use visible contamination as a parameter to monitor microbiological hygiene on carcasses at a designated critical control point in a HACCP system for red meat must be undertaken with caution. It would appear more appropriate to effect HACCP-based process control by monitoring the preslaughter presentation status of the animals, along with correct operating procedures at pelting and appropriate communication loops, rather than using on-line monitoring of the product itself for visible carcass contamination.