Effect of Natamycin and Temperature on Microbial population of Doogh during the Shelf Life

Due to development of dairy industries, consumption of Doogh in Iran as a functional fermented beverage is increasing. On the other hand in case of using the preservatives to reduce the microbial contamination in Doogh may rising the risk of chronic diseases during long time. In this study, the protective effect of natamycin as preservative on microbial population in Iranian Doogh at different storing temperatures extensively investigated. 

Microbial analyses included total count of microorganisms, population of fungi (mold and yeast), coliforms, Escherichia coli, coagulase positive staphylococci, and lactic acid bacteria on Doogh samples were extensively evaluated. 

Microbial population in Doogh samples stored at 4 °C in both treatments )with and without natamycin( was less when compare to samples stored at 25 °C and 35 °C during the shelf life period. At 25 °C, natamycin was able to significantly (P <0.05) control the growth of the wide range of microorganisms, while at 35 °C, by presence of natamycin the microbial contaminants in the majority of cases were significantly increased (P <0.05). 

According to the findings, it can be concluded that paying attention to the microbial quality of raw milk, heat treatment and cooling system during transportation, environmental hygienic conditions, as well as the storage condition of the final product at refrigerated temperatures by food retailers and consumers can effectively reduce the microbial population of Doogh and preventing the spoilage.