Survival and Growth of Listeria monocytogenes and Yersinia enterocolitica in Pork Chops Packaged under Modified Gas Atmospheres

Listeria monocytogenes Scott A, serotype 4b, and Yersinia enterocolitica from vacuum‐packaged pork were inoculated onto fresh pork chops. Survival and growth were determined in different atmospheres at 4 °C during 35‐days. Atmospheres were gas mixtures [20/0/80, 40/ 0/60, and 40/10/50 (CO 2 /O 2 /N 2 )], vacuum and air. In air L. monocytogenes and Y. enterocolitica grew slower than psychrotrophic spoilage flora. In gas atmospheres, Y. enterocolitica grew at the same rate as psychrotrophic spoilage flora and L. monocytogenes grew more slowly. When 10% O 2 was included in the 40% CO 2 mixture, growth was reduced. Vacuum packaging was no more effective than gas mixtures in retarding growth. Modified atmospheres provide an environment in the package that would allow growth of Y. enterocolitica and potentially compromise safety of meat products.