DEVELOPMENT OF Yersinia enterocolitica ON RAW AND COOKED BEEF AND PORK AT DIFFERENT TEMPERATURES

Abstract

ABSTRACT Yersinia enterocolitica counts of inoculated beef and pork as determined from confirmed isolates picked from trypticase soy agar plates were similar to the counts of confirmed enamel‐black colonies on bismuth sulfite agar plates. With three strains of Y. enterocolitica increases in count occurred on raw beef held over a 10‐day period at 0–1°C. When inoculated raw or cooked beef and pork were stored at 7°C (0–10 days) or at 25°C (0–24 hr) large increases in Y. enterocolitica count occurred. At 25°C the increases in Y. enterocolitica counts were somewhat greater on cooked than on raw products. These differences in count may have been caused by (a) differences in the physicochemical characteristics of the meat (raw vs cooked) and/or (b) differences in the level and type of microbial flora that developed on these products. In addition to Y. enterocolitica, Staphylococcus and Micrococcus spp. often were dominant on cooked products, Pseudomonas and Microbacterium spp. on raw meats.