Evaluation of the antioxidant activity during sequential hydrolysis of collagenous extracts from jumbo squid ( Dosidicus gigas ) according to the degree of collagen crosslinking and its solubility

During the processing of jumbo squid (Dosidicus gigas), a large number of byproducts are generated, one of which is a source of collagen. Through controlled hydrolysis, collagen can be used to obtain peptides with antioxidant activity. However, the magnitude of its hydrolysis depends on the degree of cross-linking of its collagen fibres. Connective tissue proteins were extracted, fractionated, and separated according to their solubility and degree of cross-linking (borate-soluble collagen (BSC) [low or not cross-linked], acid-soluble collagen [moderately cross-linked], and insoluble collagen [highly cross-linked]), followed by sequential hydrolysis using pepsin, trypsin, and chymotrypsin. The hydrolysis of BSC in connective tissue was greater. BSAC was found to have a higher percentage of antioxidant activity in the ABTS·+ (2,2-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid), with maxima of 92%. Moreover, the evaluation of antioxidant activity suggested that the lower the degree of collagen cross-linking was, the greater the degree of protein hydrolysis.