Survival of inoculated Escherichia coli O157:H7 in Japanese sweet dumplings during storage

Abstract

An outbreak of Escherichia coli O157:H7 occurred due to the consumption of sweet dumplings in Japan. We examined the survival of E. coli O157:H7 inoculated into several types of sweet dumplings to evaluate the progress of the residual contaminating pathogens after the production or packing processes. For all 4 types of tested typical sweet dumplings, no significant reduction in the viable cell counts of inoculated E. coli O157:H7 3 log CFU/g was observed during storage at -20°C and 5 for 5 weeks. Approximately 1 log CFU/g of reduction was observed after storage for 5 weeks at 10°C and 15°C, which corresponded to the growth of the naturally contaminating fungi. Similar results were obtained when we used several types of commercially distributed sweet dumplings. It is of vital importance to prevent the cross contamination of sweet dumplings after the heating process in order to reduce the risk of foodborne illness.