Antioxidant activity of tilapia (Oreochromis niloticus) skin gelatin hydrolysates and its simulated digestive products

In this paper, gelatin was extracted from tilapia skin and then separately hydrolysed by trypsin and flavourzyme.Antioxidant efficacy of respective hydrolysates were evaluated using 2, 2'-azino-bis ( 3-ethylbenzthiazoline-6-sulphonic acid) ( ABTS) radical, 1, 1-diphenyl-2-picrylhydrazyl ( DPPH) radical, hydroxyl radical scavenging and lipid peroxidation in linoleic acid inhibitory activities. The gastrointestinal digestion in vitro and molecular weight distribution of hydrolysates further evaluated the antioxidant activities. The results showed that the hydrolysis degree of flavourzyme and trypsin hydrolysates gradually increased during enzymatic hydrolysis, the highest DH values of 5.8% and 25.36% were observed in trypsin and flavourzyme hydrolysates after 3 h of hydrolysis. TCA soluble peptide content of flavourzyme and trypsin hydrolysates were higher after hydrolyzed for 60 min than other hydrolysis times, which respectively reached 56.82% and 54.44%. The gelatin hydralysates by flavourzyme and trypsin for 60 min of hydrolysis showed stronger antioxidant abilities of ABTS, DPPH, hydroxyl radical scavenging activities and anti-linoleic acid peroxidation capacity.Flavourzyme hydralysates had more potent activities on scavenging DPPH radical and inhibiting lipid peroxidation compared to trypsin hydrolysate respectively. After in vitro gastrointestinal digestion, both hydrolysates showed significant higher hydroxyl radical scavenging and lower oxidation of linoleic acid inhibitory activity ( p < 0.05) .The molecular weight distribution of the hydrolysates was mainly concentrated in 3000⁵000 Da before and after digestion in vitro. The content ( 3000 ~ 5000 Da) increased by 45% and 13% for flavourzyme and trypsin hydrolysates after digestion, respectively. These results suggested that gelatin hydrolysates, from tilapia skin, could serve as a potential source of functional food ingredients for health promotion.