Comparison of Ferrous Ion Chelating Properties of Collagen Peptides from Dried and Fresh Cod Skin

Fish skin is a potential source of collagen and collagen is a protein source of bioactive peptides including iron chelating peptides. The aim of this study is to compare physicochemical properties of collagen extracted from fresh and dried cod skin and the ferrous ion chelating properties of collagen hydrolysates. Then the fresh and dried cod skin extracted collagen was hydrolyzed with collagenase to obtain collagen peptides. The collagen peptides chelated ferrous ion. The results showed that cod skin is a good source of collagen which is accounted for 95.17% of the total proteins. The collagen from fresh cod skin was slightly easier to be hydrolyzed than that from dried cod fish. Respectively, at the same hydrolysis conditions the maximum degree of hydrolysis were 13.64 and 12.57%. The collagen from fresh cod skin had better iron chelating ability than that from dried cod skin, the iron chelating abilities were 32.16 and 23.12%. The UV-Vis spectroscopy of collagen peptides obtained from fresh or dried cod skin showed the same maximum absorption peaks near 230 and 250 nm. When combined with ferrous ion, the maximum of absorption peak is migrated. SDS-PAGE proved that the molecular weight of collagen is 180k Da more or less. The electron microscopy and infrared spectra showed that collagen peptide could chelate with ferrous ion through -NH and C = O. Fresh cod skin extracted collagen has a higher degree of hydrolysis and is more favorable to chelate ferrous ion to produce peptide ferrous chelate, but they have a similar structure.