Gelatin hydrolysates from farmed Giant catfish skin using alkaline proteases and its antioxidative function of simulated gastro-intestinal digestion

•Gelatin hydrolysates using different proteases showed antioxidant activities.•Antioxidant activity of gelatin hydrolysates increased with increasing degree of hydrolysis.•Trypsin provided the hydrolysates with high FRAP and metal chelating properties.•Visceral alkaline protease provided the lowest average molecular weight of gelatin hydrolysate.•In vitro gastrointestinal digestion, significantly improved antioxidant activities. This work aims to evaluate the ability of different alkaline proteases to prepare active gelatin hydrolysates. Fish skin gelatin was hydrolysed by visceral alkaline-proteases from Giant catfish, commercial trypsin, and Izyme AL®. All antioxidant activity indices of the hydrolysates increased with increasing degree of hydrolysis (P