Effect of time and wattage power levels of microwave treatment on the microbial quality and safety of bovine raw milk

Abstract

Raw milk is sterile when secreted by healthy cows, however it is contaminated with different microorganisms and Streptococci commonly present in the milk ducts as well as teats. The bacterial count in raw milk ranges from a few hundred to several thousand per mL of milk, however it is harmful to human health under unpasteurized condition. Milk sanitization methods rely on the principle of preventing the growth and development of microbes and thus maintaining their nutritional quality. This study was carried out to investigate the effect of microwave radiation on the microbial quality and safety of bovine raw milk. To do so, the effect of microwaves at a frequency of 35 KH and powers of 180, 300 and 850 W for 0, 30, 60 and 90 s on the destruction of pathogens and reduction of microbial load of milk (total bacterial count, coliforms, Escherichia coli, Staphylococcus aureus, molds and yeasts) was investigated. The results showed that microwave treatment had a significant effect on reducing the number of microorganisms in milk samples (p<0.0) with the power of 850 W being the most effective power for reducing the number of S. aureus, coliforms, molds, yeasts as well as total bacterial count. Faster heating with higher energy efficiency is the main advantage of the microwave process for foods. In fact, the microwave method can be a potential and effective method for decreasing the microbial load of raw milk.