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

Introduction: Due to the development of dairy industries, the consumption of Doogh has risen in Iran as a functional fermented beverage. Use of preservatives to reduce microbial contamination in Doogh could increase the risk of chronic diseases in the long run. The present study aimed to extensively investigate the effects of natamycin as a preservative on the microbial population of Iranian Doogh at various storage temperatures. Methods: Microbial analyses were performed to determine the total count of microorganisms, population of fungi (molds and yeasts), coliforms, Escherichia coli, coagulase-positive staphylococci, and lactic acid bacteria in Doogh samples. Results: The microbial population in the Doogh samples (with and without natamycin treatment) stored at 4°C was compared to the samples stored at 25°C and 35°C during the shelf life period. At the temperature of 25°C, natamycin could significantly control the growth of a wide range of microorganisms (P 0.05), while at 35°C, in the presence of natamycin, the microbial contaminants in the majority of cases were significantly increased (P 0.05). Conclusion: According to the findings, it can be concluded that paying attention to the microbial quality of raw milk, heat treatment, and cooling systems during transportation, environmental hygienic conditions and storage of the final products at refrigerated temperatures in order to effectively diminish the microbial population of Doogh and preventing spoilage is necessary.