Composition, functional properties and in vitro antioxidant activities of octopus (Octopus vulgaris) protein hydrolysates (OPHs) were evaluated. OPHs were prepared by treatment with commercial Esperase (OPH-Esp), alkaline protease extract from Zebra blenny (Salaria basilica) (OPH-ZB) and enzyme preparation from Bacillus subtilis A26 (OPH-A26). OPHs showed different degrees of hydrolysis (DH from 17.6 to 21%), and hydrophobic/hydrophilic peptide ratio. The amino acid profiles of OPHs showed a high level of essential amino acids, and Lys was the most abundant amino acid. Enzymatic hydrolysis improved solubility significantly as well as emulsifying and foaming properties of octopus proteins. The emulsifying activity index of OPHs decreased with increasing concentrations. Conversely, the foaming abilities increased as the hydrolysate concentrations increased. For the antioxidant activities, five different in vitro assay systems were investigated. All hydrolysates displayed various degrees and dose dependant antioxidant activities. The highest DPPH scavenging activity and reducing power were achieved by OPH-A26. OPH-Esp displayed the highest ability to prevent the bleaching of β-carotene, whereas OPH-ZB exhibited the highest protection against hydroxyl radical induced DNA breakage. The results suggested that OPHs could be used, as a promising source of functional peptides with antioxidant activities, to formulate functional foods.
Keywords: Antioxidant activities; Enzymatic hydrolysis; Functional properties; Octopus.