Extrusion treatment for improved physicochemical and antioxidant properties of high-molecular weight polysaccharides isolated from coarse tea

Extrusion processing was applied in pretreatment of coarse green tea and tea polysaccharide (TPS) was obtained, the physicochemical, thermal and antioxidant properties of which were comparatively studied by gas chromatography (GC), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), scanning electron microscopy (SEM). The antioxidant activity of TPS was evaluated by 1,1-diphenyl‐2-picrylhydrazyl (DPPH) radical scavenging assay. Results showed that extrusion treatment could improve the yield of TPS from 1.26% to 6.14%. The treatment resulted in the changes of TPS on the monosaccharide composition, molecular weight, thermal properties and the morphological properties. In the scavenging activity against DPPH free radicals, the TPS from extruded tea showed better activity than the untreated one. Extrusion treatment of tea could change the physicochemical properties of TPS and improve the yield and the antioxidant property of TPS, which might be helpful for the tea polysaccharide related products in the food industry.