Peptides as Related to Antioxidant Properties from Enzymatic Hydrolysates of Tilapia

Tilapia (Oreochromis niloticus) hydrolysates were prepared by the commercial enzymes Protease A, Protease N, and papain at 50℃ for 0, 3, 6, and 9 hrs. The peptide contents of the hydrolysates increased with the hydrolysis time; however, the soluble protein increased at the first 3 hrs hydrolysis and thereafter decreased. Different antioxidant measurements including the inhibition of linoleic acid autoxidation, scavenging effect on DPPH (α, α-diphenyl-β-picrylhydrazyl) free radical, and reducing power showed that tilapia hydrolysates possessed noticeable antioxidant activities. There existed a good correlation between the amount of peptides and antioxidant activity. Among the hydrolysates, papain hydrolysates for 9 hrs, had the highest inhibition of linoleic acid autoxidation and were further separated into four groups. The peptide with molecular weight of approximately 1,400 Da possessed a stronger inhibition of linoleic acid autoxidation than that of 900, 500 and 200 Da. These results indicate that enzymatic hydrolysates of tilapia protein possess potential antioxidative activity.