Characterization of pepsin-solubilised collagen recovered from mackerel (Scomber japonicus) bone and skin using subcritical water hydrolysis.

This study was aimed at isolation of pepsin-solubilised collagen (PSC) from Mackerel (Scomber japonicus) bone and skin in order to effectively valorise these abundant wastes. The yield of PSC (8.10%) from skin was considerably higher than that from bone (1.75%). Based on the protein patterns, both PSCs were type Ι, and consisted of two α-chains. Fourier-transform infrared spectra demonstrated that PSCs from the bone and skin exhibited a triple-helical structure. The denaturation temperatures (Td) of the PSCs from bone and skin were 27 and 30 °C, respectively. Low-molecular-weight peptides (<1650 Da) were generated from both PSCs after subcritical water hydrolysis treatment. Glycine accounted for 30% of the total amino acids identified in both PSC hydrolysates. The antioxidant activities of both PSC hydrolysates were significantly higher than those of the isolated PSCs. Therefore, PSC hydrolysates can be used as a functional ingredient in the food, cosmetic and pharmaceutical industries.