Abstract:In this study, single factor experiments and response surface methodology were used to optimize the conditions for ultrasonic-assisted enzymolysis extraction of polysaccharides from the raw material, Guangdong Chinese yam (CYP-UE). Then, the physicochemical characteristics (such as monosaccharide composition and molecular weight) and antioxidant activities of the Chinese yam polysaccharides obtained by ultrasonic-assisted enzymolysis extraction (CYP-UE), hot water extraction (CYP-H), ultrasonic-assisted extraction (CYP-U) or enzymolysis extraction (CYP-E) were compared. The results showed that the optimal ultrasonic-assisted enzymolysis extraction conditions were: cellulase, 8,000 U/g; pectinase, 4,000 U/g; papain, 8,000 U/g; enzymolysis temperature, 60 ℃; enzymolysis time, 90 min; ultrasonic treatment temperature, 63 ℃; ultrasonic treatment time, 48 min; ultrasonic power, 234 W. Under the optimal extraction conditions, the extraction yield of CYP-UE was 15.26%. CYP-UE had the highest yield and reducing sugar content (29.88%) among the four polysaccharides. The four polysaccharides had the average molecular weight distribution from 4.50 to 10.20 ku, and were mainly composed of glucose, galacturonic acid and galactose. CYP-UE had the smallest molecular weight (4.50 ku) and the highest percentage of glucose (96.48%). The four polysaccharides showed the characteristic absorption peaks of polysaccharides, and possessed good solution stability and solubility. The four polysaccharides had different antioxidant activities, with CYP-UE having a higher iron ion reducing power (17.08 µmol FeE/g DW) and a higher ABTS+ radical scavenging ability (IC50=2.42 mg/mL). Accordingly, the ultrasonic-assisted enzymolysis extraction can be used to prepare Chinese yam polysaccharides with a high yield and high activity.
