Heat treatment for the control of Bacillus cereus spores in foods

The effect of heat treatments on food products related to soybean curd contaminated with Bacillus cereus spores was investigated for the purpose of preventing food-poisoning outbreaks by B. cereus. In the case of B. cereus strains isolated from foods, heating foods inoculated with the spores for 20 min at 70degreesC, 5 min at 75degreesC, 2 min at 100degreesC, or (.)10 sec with a microwave oven plus reheating after standing for 2 hr at 25degreesC reduced the number of surviving cells within the foods to less than one-hundredth. In the case of a heat-resistant strain isolated from a food poisoning outbreak, heating for 20 min at 70degreesC plus reheating after standing for 1.5-2 hr at 35degreesC, heating for 10 min at 75degreesC plus reheating after standing for 1.5-2 hr at 35degreesC, or heating for 2 min at 100,C plus reheating after standing for 4 hr at 25degreesC was effective. There was not much difference between the flavor components in foods with and without heat treatment at 70degreesC, as analyzed by gas chromatography-mass spectrometry. These results indicate that these heat treatments are available to control B. cereus spores, without affecting the sensory quality of the foods.