Abstract:The ultrasound-assisted extraction process of β-glucan from Cordyceps militaris was optimized by single factor experiment and response surface methodology with β-glucan extraction yield as the main evaluation index.The chemical bonds and functional groups of the extracts were analyzed by infrared scanning，and the content of each component and its antioxidant activity in vitro were determined.The results showed that the optimal extraction process of β-glucan from C.militaris was ultrasonication time of 1 h，material-liquid ratio of 1∶31（g/mL），and temperature of 90°C.The extraction rate under the optimal conditions was（1.94±0.28）%，which was consistent with the predicted value of 1.95%.The purification test revealed that the optimal conditions for α-glucan removal were α-amylase addition of 2%，incubation time of 60 min，and temperature of 50 ℃.The purity of β-glucan increased from 19.82% to 33.93% after the purification treatment.The result of infrared scanning showed that C.militaris β-glucan had a typical polysaccharide structure with sulfate moieties.The scavenging abilities of C.militaris β-glucan on DPPH radicals，ABTS+ radicals，and hydroxyl radicals were positively correlated with the concentration（2.00-10.00 mg/mL），with IC50 values of 1.17，2.17 mg/mL and 4.35 mg/mL respectively.The scavenging rate was 100% at the concentration of 8.34，9.88 and 9.97 mg/mL.In conclusion，the optimized ultrasound-assisted extraction process of β-glucan from C.militaris was stable and feasible，and the antioxidant activity of the β-glucan extracted was good.