Abstract:With acidity，pH value，water holding capacity and sensory score as evaluation indexes，the processing parameters of Polygonatum sibiricum extract（PSE）-fermented soymilk（P-FSM）were optimized by single factor test and response surface methodology.The content of total phenols and flavonoids in the finished product was determined.The total antioxidant capacity of P-FSM was evaluated based on the DPPH-and ABTS+-scavenging rates. The content of soybean isoflavones after fermentation was determined by high performance liquid chromatography.The results showed that the optimal conditions were material-to-liquid ratio of 1∶6.4（g/mL），soybean milk-to-reconstituted milk ratio of 6∶4（volume ratio），2% PSE，6% white granulated sugar，fermentation temperature of 42 ℃，and fermentation time of 6.5 h.The content of total phenols，content of flavonoids，and antioxidant activity of the yielded P-FSM and fermented soymilk （FSM）were compared. The content of total phenols and flavonoids in P-FSM was（2.60±0.06）mg/g and（1.86±0.07）mg/g，respectively.The DPPH-scavenging rate，ABTS+-scavenging rate，iron chelating capacity，and the total antioxidant activity of the P-FSM were （57.63±0.31）%，（42.57±0.32）%，（37.43±0.59）%，and （263.40±1.67）mg/kg，separately，which were slightly higher than those of FSM.Both were assayed for soybean isoflavones after fermentation and the conversion of P-FSM to bound glycosidic isoflavones was found to be about 8% higher than that of FSM.