The study of the presence of the bacteria Bacillus cereus in milk and dairy products
1995
Godic-Torkar, K. (Ljubljana Univ. (Slovenia). Biotechnical Fac., Zootechnical Dept.)
The presence of aerobic sporeformer bacteria Bacillus cereus in milk and dairy products was established. For strain isolation and identification we used PEMBA selective medium, MPN technique, the microscope examination for the presence of spores and lipid globules, determination of hemolytic activity and mobility in solid medium and degradation of glucose in anaerobic conditions. From December to June 141 samples of pasteurized milk with 1.6, 3.2 and 3.6% milk fat, pasteurized sweet cream, curd, pudding, ice cream, milk powder, sterile milk with 1.6 and 3.2% milk fat and sterile cream were analysed. Bacillus cereus was present in 46.8% of samples and in 38.3% of samples pasteurized again. The milk powder was contaminated 100%, there were 64.0% positive samples of pasteurized sweet cream, 62.5% positive samples of curd and ice cream, 35.0 to 50.0% of pasteurized milk and 44.4% positive samples of pudding. The strains of the bacteria Bacillus cereus also appeared in 15.0% of sterile milk and sterile sweet cream. In the average the largest number of these microorganisms was found in pudding (55.4 CFU/ml), while in pasteurized milk there were only 0.08 to 0.33 CFU/ml. The seasonal oscillations with two peaks in December to January and in May to June were characteristic. The correlation between the presence of Bacillus cereus, total bacterial count, the number of psychrotrophs and sporeformer bacteria in samples were not found.
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