Preparation, functional and bioactive characterization of antioxidant and antidiabetic gelatin hydrolysates derived from bones and skins of bigeye snapper processing byproducts

This study investigated the potential valorization of processing byproducts from bigeye snapper ( Priacanthus tayenus ), particularly bones and skins, as sources of functional bioactive peptides for food and nutraceutical applications. Gelatin was extracted from fish bones and skins and used to produce bioactive hydrolysates with antioxidant and antidiabetic properties through enzymatic hydrolysis. Four hydrolysates were obtained: bone gelatin hydrolysates using alcalase (GHB-AL) and papain (GHB-PA), and skin gelatin hydrolysates using alcalase (GHSK-AL) and papain (GHSK-PA). The resulting skin and bone hydrolysate yields were 62–70% and 40–56%, respectively, with degrees of hydrolysis ranging from 48% to 74%, and a uniform color with a lightness range of 74–88. All hydrolysates exhibited high solubility (>93%) and broad pH stability (pH 1-10). The free amino acid content of the hydrolysate was higher than that of gelatin. The total amino acid content in gelatin hydrolysates was high in Gly, Ala, Pro, Hyp, Asp, Glu, and Arg. FTIR spectra showed structural similarities to gelatin, while SEM uncovered enzyme-dependent microstructural variations. All hydrolysates exhibited significantly enhanced antioxidant and dipeptidyl peptidase-IV (DPP-IV) inhibitory activities compared with gelatin. Crude hydrolysates were non-cytotoxic to Caco-2 cells (0.4-2.0 mg/mL). Simulated gastrointestinal digestion indicated that several hydrolysates retained or enhanced their bioactivities.