Purification and characterization of novel antioxidant peptides from enzymatic hydrolysates of tilapia (Oreochromis niloticus) skin gelatin

► Two enzymatic conditions of TSG were optimized by orthogonal experiment. ► A double-enzyme hydrolysis was applied to obtain the antioxidant hydrolysate (TSGH). ► Two peptides with high antioxidant activity were isolated from TSGH. ► The structures of peptides were determined as Glu-Gly-Leu and Tyr-Gly-Asp-Glu-Tyr. ► Their IC50 values on hydroxyl radical scavenging activity were 4.61 and 6.45 μg mL−1.