Food Safety Focus (192nd Issue, July 2022) – Article 3
Bacillus cereus in Fried Rice
Recently, the Centre for Food Safety (CFS) collected a sample of fried rice from a restaurant containing an unsatisfactory level of Bacillus cereus (B. cereus). Investigation by the CFS revealed that the cooked rice was left at ambient temperature for a prolonged period and this was suspected to be the reason for the unsatisfactory microbiological result.
B. cereus is a ubiquitous bacterium that can be found in soil, environment, and at low levels in raw, dried and processed food. It can form both heat-stable toxins and spores. Cooking kills the vegetative cells of B. cereus, but their spores can survive and subsequently germinate and produce toxins when the food is kept at room temperature for an extended period. B. cereus food poisoning is most commonly associated with food, such as cooked rice left at room temperature for too long after cooking. Food poisoning with freshly prepared soybean milk, and casseroles such as meat stew, curry and Poon Choi have also been reported. Therefore, to prevent B. cereus food poisoning, food not consumed immediately should be kept at safe temperatures, i.e. above 60°C or at or below 4°C. When cooling, cool cooked food as quickly as possible, for example to 20°C within two hours and from 20°C to 4°C within the next four hours.