Physicochemical and antioxidant properties of kefir from goat vs. cow milk: impact of grain concentration and fermentation time

This study aimed to compare the physicochemical and antioxidant properties of kefir prepared from Saanen goat and cow milk with 2% and 5% kefir grain concentration during 24, 48, and 72 h fermentation at 20 °C. After 72 h, the pH of the goat and cow milk kefir decreased to 4.36 and 3.89 and 4.63 and 4.27 for the 2% and 5% grain concentrations, respectively. The protein content increased in both milk types (goat: 6.79, 6.63%; cow: 4.76, 4.92%), the fat content decreased, and the alcohol content increased. DPPH, flavonoids, and total phenolic content in both the goat milk and cow milk showed dynamic fluctuations during fermentation. These changes were attributed to the metabolic activity of lactic acid bacteria, indicating the influence of milk type and grain concentration on product properties. The optimal fermentation time was determined to be 48–72 h, which can serve as a foundation for the industrial production of high-nutritional-value kefir.