Determination of microbial contamination in traditional and pasteurized butter samples, marketed in Birjand city

Butter is a dairy product made by churning fresh or fermented cream and is one of the most highly concentrated forms of fluid milk. The aim of this survey was to assess loads of microbial contamination in traditional and pasteurized butter samples marketed in Birjand city, Iran. For this propose, totally 100 samples, including 60 samples of traditional butter and 40 samples of pasteurized butter, were collected randomly under sterile conditions and were analyzed according to the protocol of Iranian National Standards Organization. Data were analyzed with SPSS-19 software. The statistical analysis of data showed that the rate of contamination with coliforms, Escherichia coli, Staphylococcus aureus and mold and yeast in the traditional butter samples were higher than Iranian Standard limits in 8.3%, 3.3%, 1.7% and 61.7%, respectively; meanwhile 7.5%, 7.5% and 27.5% of the pasteurized samples were contaminated with coliforms, E. coli, and mold and yeast, respectively. Contamination with S. aureus was not found in any of the pasteurized samples. There was no significant difference between contamination with coliforms, E. coli and S. aureus in traditional and pasteurized samples, however, this difference between mold and yeast was significant (P< 0.05). The results indicated that the microbial contamination in traditional and pasteurized butter samples was higher than standard limits in 65% and 27.5% of the samples, respectively which needs strict preventive measures