Study on optimization of ultrasonic-enzymatic extraction of polysaccharides from purple yam and its antioxidant activity

Taking purple yam as the experimental material, the extraction technology and antioxidant activity of polysaccharides from purple yam were studied by ultrasonic-enzymatic extraction, Sevag method for deproteinization, activated carbon for anthocyanins removal and in vitro antioxidant activity. Results showed that the optimum condition were as follows: cellulose amount 1.5%, material-solvent ratio 1: 10 ( g/m L) , extraction time 25 min, ultrasonic power 200 W.Under such conditions, the yield of polysaccharides was 9.83%.The mass fraction of polysaccharides from purple yam polysaccharides powder was 58.9% after deproteinization and anthocyanins removal.The extraction from purple yam showed significant antioxidant capacity, and the scavenging ability of DPPH· were weaker than vitamin C, but that of ·OH was slightly stronger than vitamin C.