A study on incidence and growth hazards of bacillus cereus in egyptian pasturized milk during refrigerator storage

الملخص EN

A total of 80 random samples, forty of each of pasteurized full cream and skimmed milk were collected from local Egyptian markets.

Samples were screened for the occurrence of Bacillus cereus.

The incidence and total count of B.

cereus in the different samples at the sterile opening were evaluated.

3 (7.5 %) B.

cereus positive samples were detected when the samples analyzed early.

All milk samples were stored at 5°C and evaluated for B.

cereus up to their expiry date (at 72°C for 15 s).

No increase in incidence and count of B.

cereus were observed during the first 8 days of storage at 5˚C but thereafter, an increase in the incidence and population of the microorganism with storage time was observed.

B.

cereus was detected in 19 (47.5 %) and 10 (25 %) of the investigated pasteurized full cream and skimmed milk samples, respectively at the end of refrigerator storage.

Quantities analysis of growth of B.

cereus in refrigerated pasteurized milk confirms that no samples achieved hygienically undesirable limit 105 cfu / ml.

Two portion of milk proved to be positive for B.

cereus were kept at ambient (25°C) and optimum (32 °C) temperatures and evaluated for the growth of B.

cereus during 24 hours.

The data indicate that, if storage temperature is abused, less than 24 h are required for low initial levels of B.

cereus cells to increase to levels that are sufficient to cause foodborne illness.

Out of 50 B.

cereus isolates tested, 48 (96 %) possessed lip lytic activity, while 30 (60 %) showed photolytic activity.

B.

cereus ability to elaborate protease and lipase may give an indication of their active role in the spoilage of pasteurized milk in abuse temperature.

In spite of the fact that the producer is responsible for the safety of pasteurized milk, it is evident that this responsibility has to be shared with the retailer and consumer by applying proper cooling, especially in the summer period.

B.

cereus role in the keeping quality and hazards of pasteurized milk were discussed.