Growth, Germination and Toxigenic Activity of Bacillus cereus in Milk Products

Growth, germination and toxigenic activity of Bacillus cereus in pasteurized milk, fruit-flavored reconstituted milk and fermented milk at 30°C were studied. Vegetative cells of B. cereus rapidly increased to 10⁸ CFU/ml in 8 h and 10⁶ CFU/ml in 12 h in pasteurized milk and fruit-flavored reconstituted milk respectively. In fermented milk, vegetative cells of B. cereus were killed or inactivated in 40 min; while about 31% of spores survived the 7 d test period. Spore germination of B. cereus was inhibited by fruit-flavored reconstituted milk and fermented milk. Chinese hamster ovary cells were transformed and/or lysed by pasteurized milk and sterilized milk with B. cereus cultured for 8 h and also by laboratory-prepared fermented milk with B. cereus introduced at the beginning of fermentation an incubated for 12 or 72 h.