VERIFICATION OF THE LEVEL OF MICROBIOLOGICAL CONTROL FOR THE SLAUGHTER AND COOLING PROCESSES OF BEEF CARCASS PRODUCTION AT A HIGH-LINE-SPEED ABATTOIR

Methods are described which were used to verify the microbiological ad equacy of the processes of production and chilling of carcasses at a h igh-line-speed abattoir. Ten excision samples (5 by 5 by 0.2 cm) were taken from each of 16 to 20 carcasses for each evaluation of these pro cesses. Twelve monthly evaluations were made for the slaughter of stee rs, heifers, and cows and additional evaluations for each of the slaug hter of cows and the chill process of carcasses. The ranges of the est imated mean log(10) most probable number of growth units per square ce ntimeter (LMPN, for 236 carcasses) and Escherichia coli per square cen timeter (LEG, for 240 carcasses) enumerated by hydrophobic-grid membra ne filter technology for the 12 monthly evaluations of the slaughter f loor were 1.11 to 1.62 (LMPN) for single samples and 0.20 to 0.65 (LEG ) for pooled samples. Based on a published advisory scale for the slau ghter floor the aerobic bacterial counts reflect a cleanliness level o f ''excellent'' to ''good.'' For single evaluations of cow carcasses a t the end of slaughter and of chilled carcasses the mean LMPN was 1.78 (''good'') and 1.40 respectively. From pooled samples of each of the 236 steer, heifer, and cow carcasses the pathogen E. coli O157:H7 was identified by polymerase chain reaction on one carcass whereas Listeri a monocytogenes was identified on 14 carcasses. Verocytoxigenic E. col i (6 isolates) and L. monocytogenes were not isolated from the same ca rcasses. These low isolation rates dictate a large sample size and the refore these pathogens are excluded from use to routinely verify the w orkings of hazard analyses and critical control point (HACCP) systems for beef slaughter processes in Alberta. Alternatively the use of aero bic bacterial counts to directly measure cleanliness or of E. coli cou nts to indirectly measure fecal contamination appears to be more pract ical than the use of specific pathogen counts for regulatory agencies to verify the workings of quality control programs, including HACCP sy stems.