Study on Extraction Process Optimization, Structure Identification and Functional Activity of Polysaccharide from Sweet Potato Residue

In this study, ultrasonic assisted hot water extraction was used to extract crude polysaccharides from sweet potato residue. Single factor experiments and response surface optimization were used to extract the technological parameters. The polysaccharides from sweet potato residue were obtained by enzymatic deproteinization, H₂O₂ decolorization and Superose 12 10/300 GL gel column. The structure of sweet potato residue polysaccharide was identified by ultraviolet spectroscopy, infrared spectroscopy and HPLC. On this basis, the antioxidant activity and hypoglycemic ability of sweet potato residue polysaccharide were determined in vitro. The experimental results showed that the optimum extraction conditions of polysaccharide from sweet potato residue were extraction temperature 70 ℃, ultrasonic power 264 W, extraction time 56 min and solid-liquid ratio 1:17 g/mL. under these conditions, the yield of polysaccharide was 5.053%. Infrared identification showed that the polysaccharide was α-glucopyranose was determined by HPLC. It was composed of 9.46% mannose, 4.28% rhamnose, 11.72% glucuronic acid, 62.37% glucose and 10.58% xylose. The IC₅₀ values of DPPH·, ·OH and superoxide anion scavenged by sweet potato residue polysaccharide were 3.089, 4.879, 5.832 mg/mL respectively, the IC₅₀ values of α-amylase and α-glucosidase were 7.674 and 18.961 mg/mL, respectively. In summary, the sweet potato residue polysaccharide had good antioxidant and hypoglycemic activities. The above results would provide data reference for the purification, functional activity analysis and comprehensive utilization of sweet potato residue polysaccharide.