Fate of <i>Escherichia coli </i>O157 Spiked into Commercially Available Fermented Soybean Paste (miso)

Abstract

This study investigated the fate of Escherichia coli (E. coli) O157 spiked into 24 commercially available fermented soybean paste (miso) samples. Viable cell numbers of the inoculated E. coli O157 at storage conditions of 5, 10, 20, or 30 ℃ were measured by the agar plate method or most probable number method. Cell numbers of E. coli O157 decreased gradually in all tested samples. The decreases in E. coli O157 numbers depended mainly on the water activity of samples. Decreases in the contamination level of E. coli O157 did not depend on the ingredients of miso samples (malted rice, wheat, and soybean). The obtained results suggest that the commercial risk of accidental E. coli O157 contamination is practically negligible because of high cell mortality during transportation and storage processes at room temperature.