Isolation and purification of soybean antioxidant peptides

The soybean protein was hydrolyzed by Alcalase Food grade (FG) 2.4 L and the degree of hydrolysis (DH) were determined. The DH increased with the hydrolysis time increasing during 3.0 h. Then the hydrolysates was isolated by ultrafiltration membrane (1, 3, 10 kDa) and antioxidant activity was evaluated based on DPPH radical scavenging activity. The fraction of 1-3 kDa possessed the higher antioxidant activity than the other fractions (P < 0.05). Sephadex G-25 gel column was used to purify the three kinds of peptides and the eluted volume was investigated.