Yam Mucilage Powder Characteristics And Its Application Research In Fermented Yogurt

Yam mucilage is rich in functional components and possesses special viscosity and various functional effects.In this paper,we first explored the composition,viscosity and antioxidant activity of Chinese yam mucilage.We then applied mucilage powder in yogurt and optimized the process conditions using central composite experiment.(1)The results show that yam mucilage contains 72.25% of sugars and 25.25% of proteins.The former contains 51.39% of polysaccharides,45.99% of glucose,32.16% of mannose,11.41% of galactose,3.69% of galacturonic acid,3.61% of arabinose and 3.14% of glucuronic acid,as measured by ion chromatography analysis.Lyophilization of yam mucilage powder reduces its reductive ability and weakens its scavenging ability of free radicals DPPH,hydroxyl and superoxide anion to some extent,but showing no significant difference from the fresh samples.In addition,the viscosity of yam mucilage aqueous solution increases gradually with the increase of its concentration,but decreases with temperature increasing.Moreover,the viscosity of yam mucilage aqueous solution is 1.033 Pa·s at pH 6,1.246 Pa·s at pH8 and decreases when pH is beyond this range.Heat treatment decreases the viscosity of yam mucilage and this decrease is more obvious with temperature and time increasing.(2)Addition of appropriate amount of mucilage powder significantly affects the acidity,pH,water retention and sensory index of yogurt and improves the quality of yoghurt.The response surface optimization found that the amount of mucilage powder has the greatest influence on the quality of yogurt and the best fermentation conditions are ratio of milk powder to water of 1:7,the amount of yam mucilage powder of 1.6%,the sugar quantity of 7.1%,the inoculation quantity of 4.9% and fermenting 5.9 h at 42oC.The product sensory score is 91.53.(3)The sensory indexes,physical and chemical indexes and hygienic indexes of yam mucilage yogurt under the optimum technological conditions meet the standard for fermented milk.Compared with ordinary yogurt,addition of 1.6% mucilage powder significantly improves the antioxidant activity of yogurt in vitro,which is of great significance for the development of mucinous healthy yogurt.Meanwhile,yogurt with yam mucilage has longer storage period at 4oC and better indexes and sensory scores than those without addition of yam mucilage.