Abstract: This paper reports an ultrasound-assisted enzymatic method for the extraction of soluble soybean polysaccharides. On the basis of single factor experiments, four crucial extraction parameters such as material/water ratio, ultrasonic power, extraction temperature and cellulase amount were optimized for maximizing the yield of soluble soybean polysaccharides using a four-variable, five-level quadratic rotation combination experimental design. Subsequently, the in vitro antioxidant activities of soluble polysaccharides extracted from soybean dregs were evaluated by hydroxyl radical, superoxide anion radical and DPPH radical scavenging assays. The maximum extraction yield of soluble polysaccharides from soybean dregs, 9.32%, was obtained after 20-min extraction under the optimal conditions: material-to-liquid ratio 1:25 (g/mL), ultrasound power 700 W, temperature 50 ℃ and cellulase amount 30 U/g. The resulting extract exhibited obvious scavenging activity against hydroxyl, superoxide anion and DPPH free radicals in a concentration-dependent manner.

Key words: soluble soybean polysaccharide, soybean dregs, antioxidation, ultrasound-assisted enzymatic extraction