Use of Petrifilm^™ 3M to Assess Coliform Numbers on Lamb Carcasses

Petrifilm^™ (6410) was used directly on lamb carcasses to enumerate coliforms. Ten sampling locations (sites) on 30 carcasses were sampled at each of four separate meat processing establishments (works). The coliform counts obtained by this technique were statistically analyzed using analysis of variance (ANOVA) to select the optimum sampling sites on the carcass and to assess the contamination of the carcass by gut flora at a particular establishment. There was a large variation between sites and between works. In general, works 3 and 4 produced cleaner carcasses than works 2, which in turn was cleaner than works 1. Since works 1, 2 and 4 used conventional dressing techniques and works 3 used the inverted dressing method, the coliform counts found at works 3 and 4 are achievable regardless of dressing technique. The coliform bacteria were most concentrated around the posterior pelvic rim and least prevalent at the carcass extremities. The posterior pelvic rim (sites 3 and 4) had higher (P<0.05) coliform counts than the exterior ventral flank area (sites 5, 6, 7 and 8), which in turn had higher (P<0.05) counts than the proximal hind and proximal fore limbs (sites 1, 2, 9 and 10) across all works. With in-line routine testing it is recommended that the majority of carcasses sampled should give coliform counts of less than 50 colony forming units (CFU)/20 cm² for sites 4 and 8.