Effect of different stabilizers on the quality and flavors of set-style yak yoghurt during post-fermentation storage

The objective of this study was to investigate the effects of xanthan gum,pectin and CMC-Na on quality and flavors of set-style yak yoghurt during post-fermentation storage. The sensory scores,acidity,water holding capacity and texture characteristics of yak yogurt with adding different stabilizers were measured,and volatile flavor compounds of yak yogurt during different post-fermentation time were analyzed. The results showed that different stabilizers had different effects on the sensory,physical and chemical properties and texture of yak yogurt. The addition of xanthan gum,pectin and CMC-Na had significant influence on the sensory,acidity and water holding of yak yoghurt(p<0.05),and improved the hardness of yogurt to some extent,but excessive amount of stabilizers could reduce the viscosity of yoghurt. The optimal combination of stabilizers determined by orthogonal test was 0.04% pectin,0.02% xanthan gum and 0.03% CMC-Na, the water holding capacity of yak yoghurt prepared by this stabilizer was 71.52% and the sensory score was 42. Determination of volatile flavor compounds in yak yoghurt showed that alcohol was the highest content of yak yogurt,followed by ketones and other types(mainly aromatic),again for the aldehydes. With the extension of post-fermentation time,the amount of volatile flavor substance in the blank group had small changes. On the second day of post-fermentation,the flavor stabilizing effect of pectin group was the best,followed by CMC-Na,the effect of the compound stabilizer group was the worst. The flavor stabilizing effect of the composite stabilizer group was the best on the seventh day of post-fermentation compared with the second day.