Extraction And Activity Of Polysaccharide From Yam (Dioscorea Opposita) By-Products

Dioscorea opposita, also named Chinese yam, belongs to Dioscoreaceae plants, which is used both as medicine and food. Ruichang yam by-products was used as raw materials in this research, the extraction, rheological property and biological activities of polysaccharides from yam by-products were investigated. The instant sheet added with yam polysaccharide which was rich in nutrition. The main content and conclusions were as follows:On the basis of single factor experiment, the mathematical regression model about the independent variables(extraction temperature, extraction time, liquid-solid ratio) was established and response surface method was used to optimize the extraction technology of yam polysaccharide. Two different extraction methods were compared to find the best extract technology. The results showed that the ultrasonic-assisted water extraction method was better than the inner ebullition method considering the polysaccharide yield, the optimum extraction process was as follows: extraction temperature of 93℃, the liquid-solid ratio of 1:15 and extraction time of 97 min, the yield of polysaccharide under the optimal conditions reached 3.14%; the optimum extraction process of the inner ebullition method was as follows: extraction temperature of 86℃, the liquid-solid ratio of 1:22, and extraction time of 10 min, the yield of polysaccharide under the optimal conditions reached 2.99%. Although the polysaccharide yield of the ultrasonic-assisted inner ebullition method is slightly lower than the ultrasonic- assisted water extraction, the ultrasonic-assisted inner ebullition method greatly save the time.Viscometer method was used to study the viscosity of polysaccharide under the different conditions(heat treatment temperature, p H, heat treatment time, the effect of salt concentration). Heat treatment temperature increased from 30℃ to 100℃, and the viscosity of the solution decreased from 3.7 mPa.s to 2.4 mPa.s, the viscosity of polysaccharide was more sensitive to the change of pH, and the viscosity of polysaccharide could be decreased by both acid and alkali, pH increased from 2 to 10, and the viscosity of the polysaccharide increased from 3.6 mPa.s to 4.9 mPa.s, besides, the viscosity of polysaccharide decreased gradually with the increase of temperature and the heat treatment time.The inhibition of polysaccharide on a-amylase activity in vitro was studied. The investigation shows that the water extraction method and the inner ebullition method have a certain inhibitory effect on a-amylase activity, polysaccharide concentration on the inhibition of the a-amylase activity showed a significant dose dependent relationship, with the increase of dose, the inhibition rate also increased. With the improvement of the purification degree of polysaccharide, the inhibition of polysaccharide on a-amylase activity was also increased. When the concentration of polysaccharide comes to 2.5mg/m L, the inhibition rate of WE1 was 11.66% and the inhibition rate of IEE1 was 13.83%. Obviously, the activity of polysaccharide obtained by inner ebullition method was higher than that of water extraction method.The scavenging nitrite and blocking nitrosamine synthesis research of yam polysaccharide in vitro were studied, results showed that the yam polysaccharide has certain ability to remove nitrite and block the synthesis of nitrosamine. In mimic gastric juice environment, the clearance rate of polysaccharide up to 13.75%, the blocking rate of polysaccharide up to 24.59%. The scavenging and blocking ability were also studied in non mimic gastric juice environment, the clearance rate of polysaccharide up to 10.58%, the blocking rate of polysaccharide up to 37.33%. In the two systems, the clearance rate and blocking rate were all related to the concentration of crude polysaccharide, and the reaction time showed a significant dose effect relationship with the clearance rate and blocking rate, the clearance rate of polysaccharide in non mimic gastric juice environment were significantly lower than that in simulated gastric juice environment. The results showed that the acid conditions were more favorable for the removal of nitrite. The blocking rate of polysaccharide under simulated gastric juice environment was slightly lower than that under the non simulated gastric juice environment, which might be due to the easier synthesis of nitrite under the acidic conditions.The instant sheet with yam polysaccharide was developed and the product which is more in line with the requirements was obtained: HPMC(1 g), CMC(2 g), yam polysaccharide(1 g), glycerol(1 mL), Tween-80(0.2 m L), Gardenia Yellow(3 mg), stevioside(0.02 g), xylosic alcohol(0.3 g), mannitol(0.1 g). The results showed that the product both taste and physical and mechanical properties are better, can meet the needs of the consumer market.