Screening Of Lactic Acid Bacteria For Soymilk Fermentation And The Study On Antioxidant Properties Of Fermented Soymilk

Soymilk was full of functional ingredients such as soybean isoflavone and soybean protein.After fermentation,the glycosidic soy isoflavones of soymilk was converted to aglycone soy isoflavones.The antioxidant activity of the fermented soymilk was better than soymilkIn this study,soymilk was fermented with 5 lactobacilli strains(L.casei 16,L.sakei B2-4,E.gilvus B2-10,L.plantarum S2-6,L.plantarum Y3-1)and the antioxidant activity and the soy isoflavones of the fermented soymilk was studied.The acid production ability of L.casei 16 and L.plantarum Y3-1 were the best in the 5 strains.The pH of the soymilk fermented by them for 12 h were both 4.05.The ?-glucosidase activity of the soymilk fermented by L.casei 16 for 24 h was 74.32 mU/ml,significantly(p<0.05)higher than those of the soymilk fermented by other four strains.It means that L.casei 16 has a better conversion effect on glycosidic soy isoflavones.And the DPPH free radical scavenging of the L.casei 16 fermented soymilk was 94.38 %,higher than those of fermented soymilk by other four strains.The L.casei 16 fermented soymilk was analyzed by HPLC.The concentrations of the genistin and daidzein of the L.casei 16 fermented soymilk was 12.497±0.188 ?g/mL and 13.096±0.241 ?g/mL,significantly(p<0.05)higher than those of the unfermented soymilk.This shows that the acidification activity of L.casei 16 fermented soymilk is related to free soybean isoflavones.The ORAC(Oxygen Radical Absorbance Capacity)of the alcohol extract of soymilk fermented by L.casei 16 was 384.13±57.74,significantly(p<0.05)higher than those of the aqueous extract of the fermented soymilk and the alcohol extract and aqueous extract of unfermented soymilk.The alcohol extract and aqueous extract of soymilk fermented by L casei 16 could enhance the survival rate of the HepG2 cells damaged by 2,2'-Azobis(2-amidinopropane)dihydrochloride(AAPH).They could increase the activity of the Superoxide Dismutase(SOD)on AAPH-induced HepG2 cells.(p<0.05)These show that L.casei 16 fermented soymilk cound eliminate free radic,and it can also increase antioxidant enzyme activity in the body.