Abstract: In this study, gelatin was extracted from the skin of New Zealand hoki (Macruronus novaezelandiae), and was further hydrolyzed enzymatically to produce peptides. Peptide-selenium complexes were prepared by using sodium selenite as a selenium source and the one with high selenium-binding capacity was selected and structurally characterized. The results indicated that the pepsin hydrolysate had the highest calcium binding capacity (13.61 μg/mg) and was thus used to peptide-selenium complexes. After selenium binding, the UV absorption intensity of the peptides increased, accompanied by a red shift in the maximum wavelength, and the fluorescence absorption peak shifted from 311 to 355 nm together with a weakening of the fluorescence intensity. These phenomena indicated the production of a new complex from selenium binding to the peptides. Based on particle size distribution measurement, atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray diffraction analysis, the peptide-selenium complex had a nanocrystalline structure. The binding reaction of carboxyl and amino groups in the peptides with selenium transformed the secondary protein from β-sheet to α-helix and β-turn, thereby making the structure more compact and orderly. This study provides a new approach for high-value utilization of fish skin.

Key words: hoki skin; gelatin polypeptide; selenium; peptide-selenium complex; structural characterization