Effect of Fermentation and Post-fermentation on Nutritional Composition and Volatile Substances of Yak Milk

Abstract

In order to investigate the nutritional composition and volatile substances of yak milk after fermentation and post-fermentation, the changes of nutrients and volatile substances of yak milk, fermented yak milk and post-fermented yak milk were measured, and the nutrition and quality of yak milk were evaluated. The results showed that the lactose content of yak milk after fermentation was significantly decreased (P 0.05), but the types and relative contents of alcohols, aldehydes and esters in yak milk after ferentation were greatly decreased. There were no significant differences in lactose, amino acid and fatty acid contents between post-ferentation and ferentation of yak milk (P > 0.05), but the types and relative contents of alcohols, phenols, esters and ketones in post-ferentated yak milk greatly increased compared to fermented yak milk. In summary, fermentation improved the nutritional value of yak milk in some extent, and post-fermentation promoted the accumulation of volatile substances of yak milk. Fermentation and post-fermentation had positive effect on the improvement of nutrition and quality of yak milk.

Keywords

• yak milk
• fermentation
• post-fermentation
• amino acid
• fatty acid
• volatile substances