Enzyme and Microwave Coassisted Extraction, Physicochemical Properties, and Antioxidant Activity of Polysaccharides from Baijiu Distillers' Grains

Baijiu distillers' grain is a solid waste after the fermentation of grains, and their high added value and deep processing and utilization require further study. This study uses the enzyme and microwave coassisted method to extract Baijiu distillers' grain polysaccharides (DGPs). Through optimization of the single‐factor test and response surface methodology (RSM), the optimal conditions are solid–liquid ratio 1:30, enzyme time 50 min, enzyme temperature 50 °C, enzyme pH 5.0, microwave time 6 min, and microwave power 480 W, with a maximum DGP yield of 3.98% ± 0.03. DGP is purified by DEAE‐Sepharose cellulose ion exchange chromatography to obtain four fractions, namely DGP‐1, DGP‐2, DGP‐3, and DGP‐4; the molecular weights are 2224.05, 90.99, 1478.16, and 346.19 kDa, respectively, and the main monosaccharide components are Man and Glc. The antioxidant assay shows that the four kinds of DGPs have different free radical scavenging capacities, among which DGP‐2, DGP‐3, and DGP‐4 have good antioxidant activities. Therefore, DGP can be used as a potential natural antioxidant.