Evaluation of the Bacteriological Safety of Low-Salt Miso

Studies were done to evaluate the safety of three different low-salt (2.36 to 5.79% NaCl) misos inoculated with different bacterial pathogens. Clostridium botulinum types A and B (inoculum level of ca. 120 spores/g) did not produce toxin in any of the misos within 18 wk at 25°C. Staphylococcus aureus , Salmonella typhimurium and Yersinia enterocolitica (inoculum level of ca. 10³ to 10⁴ CFU/g) progessively died in all of the misos held at either 10 or 25°C. The miso samples, which were obtained from Japan (3.75 and 5.79% NaCl) and California (2.36% NaCl), had water activities of 0.843, 0.835 and 0.875, respectively, and pH values of 5.26, 5.30 and 4.73, respectively. Results indicate that low-salt misos with these properties are not likely to be bacteriological health risks.