Effects of Ethanolic and Aqueous Extracts of Propolis on the Microbial Load of Raw Milk

Propolis is one of the most important bee byproducts that, due to its high antimicrobial properties, has the potential to be used as a food additive. This study investigated the effects of aqueous and ethanolic extracts of propolis on the microbial load of raw milk.

Raw milk samples containing0.1, 0.5, 1, and 2% ethanolic extracts and 0.5, 1, 3, and 5% aqueous extracts were prepared. The treatments were incubated at 4 °C and 25 °C and were cultivated by pour-plate technique in PCA medium during storage times of 0, 2, 24, 48, and 72 hours. By a total count of microorganisms, the effects of different concentrations of propolis extracts on the microbial load of raw milk were investigated. The chemical compounds of the extracts were identified by gas chromatography–mass spectroscopy (GC-MS) analysis.

At 25 °C, all concentrations of aqueous and ethanolic extracts affected the microbial load of raw milk, but at low concentrations, such effects were observed after 24 hours. Aqueous and ethanolic extracts of propolis at 25 °C compared to 4 °C in lower concentrations showed more antimicrobial activity. It was also found that propolisextracts need time to exhibit high antimicrobial activity. Forty-onecompounds were identified with the dominance of phenolic and flavonoid compounds. Discussion and

The antimicrobial properties of the tested propolis extracts can be attributed to the high amounts of phenolic and flavonoid compounds and the use of this bee product as an additive is recommended.