Bacteriological study of raw and unexpired pasteurized cow's milk collected at the dairy farms and super markets in Sari city in 2011

INTRODUCTION The quality of milk is influenced by different bacteria present in milk. This study was undertaken to investigate the bacterial contamination of raw and pasteurized milk in Sari Township, Iran, 2011. METHODS In this investigation, 100 pasteurized milk samples were collected randomly from the super markets in the city and 100 raw milk samples from 4 dairy farms from suburb areas and evaluated for the presence of coliforms, Escherichia coli, Staphylococcus aureus and Listeria monocytogenes by culture methods and biochemical tests. Data analysis was performed by SPSS software using Chi2 test and described in percentage. RESULTS In the raw milk, contamination with E. coli, coliforms and Staphylococcus aureus was observed in 42 (42%), 36 (36%) and 22 (22%) of samples respectively, and the same for the pasteurized milk samples was 9 (9%), 2 (2%) and 2 (2%), respectively. Listeria monocytogenes was not detected in any sample. Presence of E. coli in the milk could be due to contamination with waste water and fecal materials. CONCLUSIONS Considering the contamination of raw and pasteurized milk with E. coli and coliforms, sanitary practice during collecting and transporting, particularly in the summer season is recommended.