activity of Bacillus cereus isolated from refrigerated dairy products

ABSTRACT. The present study evaluated the incidence of B. cereus in samples from 85 refrigerated dairy products through inoculation in selective medium and confirming according to biochemical proofs. Confirmed strains were then inoculated in specific growth medium at 7, 10 and 30°C to test the psychrotrophic behavior, and lipolytic and proteolytic activity. B. cereus was found in 15 of the 85 samples (17.6%); and 12 of them (80%) were let to grow up at 10°C for 7 days. When incubated at 7°C for 10 days, four strains (26.7%) grew up. All isolated B. cereus strains have shown proteolytic activity at 30°C, and 5 (33%) also presented lipolytic activity. At 10°C for 7 days, six strains (40%) showed proteolytic activity, and only one (6.7%), lipolytic activity. The temperature of 7°C for 10 days inhibited the production of proteases and lipases by the strains. The present work confirmed the presence of B. cereus strains with psychrotrophic, proteolytic and lipolytic activities in dairy products, which represents a potential risk for products stored under refrigeration