Abstract: In this research, we optimized the preparation conditions of Fe2+-chelating peptides from tilapia skin protein, and we structurally characterize the complex. Five commercial proteases were screened for the highest Fe2+-chelating rate of peptides. The effects of chelating time, pH and temperature on the Fe2+-chelating rate were evaluated, and the changes in the fluorescence, ultraviolet and infrared spectra of the peptides were examined before and after chelating with Fe2+. In addition, the molecular mass distribution, amino acid composition and antioxidant activity of the peptides were measured. The results showed that the peptides obtained after 2 h of hydrolysis with trypsin had the highest Fe2+-chelating rate. The optimal chelating conditions were pH 5, 37 ℃, and 90 min. Chelating with Fe2+ resulted in folding of the peptide chain, decreased intrinsic fluorescence intensity, and red shift of the characteristic ultraviolet absorption band. Fe2+ was likely bound to the amino, carbonyl and carboxyl groups of the peptides. The molecular mass of the Fe2+-chelating peptides was about 500–3 000 Da, and the peptide chains were rich in Asp, Glu, Gly, Arg and Pro. All hydrolysates had antioxidant capacity. The antioxidant capacity was not significantly changed after chelating with Fe2+. Although the antioxidant capacity of the trypsinic hydrolysate was significantly lower than that of glutathione, the Fe2+-chelating activity was significantly higher than that of glutathione. The results showed that the peptides in the hydrolysate had excellent Fe2+ -chelating activity suggesting the potential to be developed into a new dietary iron supplement.

Key words: tilapia skin protein; peptide-Fe2+ complexes; chelating conditions; structural characteristics; biological activity