A risk assessment study of Bacillus cereus in packaged tofu at a retail market in Korea.

The objective of the study was to conduct a quantitative microbial risk assessment of Bacillus cereus for packaged tofu in Korea. Packaged tofu, including soft and firm tofu from six retail markets in Korea, were monitored to determine the initial contamination level of B. cereus. Predictive growth and survival models were developed to predict the change in B. cereus populations as a function of time and temperature (4-45 °C) from market to home. B. cereus was detected in 11 (12.9%) samples among 85 samples purchased at retail markets, and the average contamination level was 1.84 log CFU/g. Growth of B. cereus in tofu was observed at a temperature above 11 °C. The probability risk of B. cereus diarrheal illness due to packaged tofu consumption at the retail market is 1.0 × 10-4 per person per day. Key risk factors at the retail market and home are storage temperature and time of packaged tofu.