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Contamination of raw milk and several milk products with Bacillus cereus, was investigated on KG agar. The effects of low pH on the growth and spore formation of B. cereus was also investigated in Tryptic Soy broth. The average contamination of B. cereus in raw milk of farm and of bulk raw milk in the factory was 2.30 X 10³ cfu/㎖ and 1.96 X 10³ cfu/㎖, respectively. The contamination reached the peak in August, then gradually decreased. Contamination of B. cereus was less than ten per ㎖ in market milk and was increased in July and August, and then decreased after September. In dried milk products, contamination of B. cereus was 8.7 X 10² cfu/㎖ and reached the peak in August, then decreased sharply after September. B. cereus LDTM04 was able to grow in Tryptic Soy broth aerobically above pH 4.6 but the growth was not observed below pH 4.2. When the culture broth of B. cereus LDTM03 and B. cereus LDTM04 was adjusted to pH 4.5 after 2, 4, and 6 hours after incubation, viable cells and number of spores decreased immediately, then number of spores was not changed at least for 10 hours of incubation. Therefore pH 4.5 was thought to be a limit pH for the growth and the sporulation of B. cereus.
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