Jujube Syrup and Starter YF-L922 Co-Fermentation of Yak Yogurt: Effects of Quality Properties, Antioxidative Activities and Structure.

Different percentages of jujube yrup (0%, 3%, 6% and 9%) were incorporated into yak milk and fermented using the fermenting agent . The quality characteristics and antioxidant activity of the resulting yogurt were evaluated at days 0, 7, 14, 21 and 28. The results indicated that the pH and acidity of the yogurt were not significantly influenced by the varying additions of jujube syrup during storage ( > 0.05). However, the addition of jujube syrup significantly reduced the water-holding capacity of the yogurt ( < 0.05). Furthermore, the levels of jujube syrup were significantly and positively correlated with both antioxidant activity and free radical scavenging ability ( < 0.05). The live bacterial count of the yogurt decreased significantly by day 28, although the count of live lactic acid bacteria remained above 10 CFU/mL. Notably, yak yogurt with a 3% addition of jujube syrup achieved a favorable sensory score. The incorporation of jujube syrup resulted in a firmer texture and a more porous microstructure, demonstrating a higher degree of syneresis. Additionally, the inclusion of jujube syrup substantially diminished the animalic odor associated with yak milk, improved flavor acceptability and enhanced the antioxidative properties of yak yogurt. Therefore, yak yogurt augmented with jujube syrup represents a novel product with high nutritional value.