Development and characterization of gelatin peptides and peptide‑calcium chelates from tuna processing by-products of skins and bones.

This study used hydrothermal extraction to obtain gelatin from tuna processing by-products. After treatment, the yield (w /w dry weight) of gelatin from skins and bones were 70.22 ± 2.07 % and 28 ± 3.03 %, respectively. Enzymatic hydrolysis using alkaline protease and pancreatin converted the gelatins into peptides, with the content of oligopeptide up to 87.67 ± 1.44 %. The tuna bone gelatin peptides exhibiting higher scavenging abilities against hydroxyl radicals (·OH−), 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH ·), and hydrogen peroxide (H 2 O 2) compared to tuna skin gelatin peptides. Gelatin peptides were chelated with CaCl 2 at 50 °C for 60 min, pH 8.0, and a 1:2 peptide-to‑calcium ratio, achieving a maximum calcium binding capacity of 56.70 ± 1.67 %. Fourier-transform infrared spectroscopy indicated the participation of amino and carboxyl groups in the reaction. These findings provide technical and theoretical support for the development of calcium-chelated gelatin peptides. • The amino acid composition of tuna skin and fish bone gelatin was clarified. • Collagen polypeptides with high antioxidant activity were prepared. • The method of chelating collagen polypeptides with calcium was established. • The structure of peptide-calcium chelates were identified and analyzed by infrared. [ABSTRACT FROM AUTHOR]