Effect of Storage Conditions on Growth of Heat-Stressed Yersinia Enterocolitica in Ground Pork

Abstract

Ground pork was inoculated with either heat-shocked or non-heat-shocked (control) Yersinia enterocolitica. After thorough mixing, the meat was divided into 25-g portions in plastic pouches and sealed under air, vacuum, or modified atmosphere (50% CO2 and 50% N2). All the samples were heat-treated at 55°C for 15 min and then stored at either 25 or 4°C. Samples were plated at regular intervals after storage and the growth of Y. enterocoliticawas determined. Survivors were also examined for pathogenicity by performing certain biochemical assays. The growth of Y. enterocolitica, both heat-shocked and control, was observed under all atmospheres and both temperatures. There was no significant difference in growth rates between the heat-shocked and control samples under all the storage atmospheres and temperatures. Also, in both heat-shocked and control samples, Y. enterocolitica grew rapidly under all atmospheres, and the survivors remained pathogenic. The results indicated that storage of meat at 4°C, whether under vacuum or modified atmosphere, was insufficient to inhibit growth of Y. enterocolitica and that prior heat shock had no effect on growth rate or pathogenicity of survivors.