In Vitro Antioxidant Activities of Protein Hydrolysate from Germinated Black Soybean (Glycine max L.)

During this study, the effect of germination in combination with in vitro pepsin and pancreatin digestion of protein flours extracted from black soybean on the production of bioactive peptides was investigated. Black soybean (Glycine max L.) were germinated for 3 days (at 24, 48 and 72 h, respectively germination periods) and harvested. Protein hydrolysates from germinated black soybean were prepared from protein isolate by in vitro digestion using pepsin and pancreatin and then evaluated for antioxidant activity. Soy protein hydrolysate from 48 h of germination exhibited the highest scavenging activity against 2, 2-Diphenyl-1-Picrylhydrazyl (DPPH) free radicals (76.56 % at 2.5 mg/mL) followed by 24 and 72 h (66.62 and 60.55% at 2.5 mg/mL, respectively). Protein hydrolysate from germinated black soybean also exhibited noticeable scavenging activity for hydroxyl. Soy protein hydrolysate from 48 h of germination (97.475% at 2 mg/mL) significantly was the most effective in neutralizing OH (p<0.05) than that from 24 and 72 h (88.56 and 92.5%, respectively at 2 mg/mL), compared to the nongerminated which was 34.42% also at the same concentration. In addition, soyprotein hydrolysate from 24 h of germination significantly showed the highest reducing power (0.32 at 2.0 mg/mL) compared to that from 48 and 72 h germination period (0.25 and 0.23 at 2.0 mg/mL, respectively). Molecular Weights distribution of protein hydrolysates from germinated black soybean was believed to have correlation with their antioxidant activities. Results showed that germination with in vitro digestion (pepsin and pancreatin) of protein hydrolysate from germinated black soybean was successful in production of natural antioxidant compounds which established obvious antioxidant potency than non-germinated. As conclusion, soy protein hydrolysate from 48 h of germination had the best antioxidant potency and could be used as natural antioxidant in food systems.