Occurrence of Bacillus cereus in raw milk receiving from UF-Feta Cheese Plants

Milk and milk products are very suitable medium for growing microorganisms (e. g. Bacillus cereus). B. cereus is spore former bacilli، which easily survives during pasteurization and makes several problems in dairy industries. The aim of this study was to investigate aerobic spore and B. cereus of receiving raw milk from three UF plants.

Samples were gathered from raw milk transport tankers arrived to plants during 30 days in winter. Also، the swab test was used for detection of B. cereus residual on milk contact surfaces.

High contamination level of aerobic spores (AeSC) and especially B. cereus were found in most samples compared with the criteria established by national and international standards. Although total viable count (TVC) in samples from industrial farms (IF) was lower than those from traditional farms (TFs) and milk collection centers (MCCs)، considerable AeSC and B. cereus were transmitted to the UF plants from IFs. The highest and lowest TVC and B. cereus were found in samples from IFs and MCCs، respectively. In addition، our investigation in IFs revealed that teats contamination to soil and feces، as well as contaminated bedding might were the most important sources of B. cereus and AeSC of raw milk. Moreover، the results of swab tests confirmed that the “cleaning in place” system may not remove B. cereus effectively.

It seems that for classifying raw milk quality، AeSC might be used as a more effective quality factor than TVC. Management commitment is effective to improve quality by balance between the amount and quality of receiving raw milk. This leads to the lower contamination in dairy plants and final products.