Active oxygen scavenging activity of egg-yolk protein hydrolysates and their effects on lipid oxidation in beef and tuna homogenates

Egg-yolk protein hydrolysates were prepared by the enzymic hydrolysis of fat-free egg-yolk protein. The active oxygen scavenging activity, of egg-yolk protein hydrolysates, was investigated using several methods. Egg-yolk protein hydrolysates suppressed discoloration of β-carotene, strongly as compared with the control in β-carotene bleaching method. Superoxide-scavenging activity of egg-yolk protein hydrolysates was measured using the xanthine–xanthine oxidase system. Egg-yolk protein hydrolysates exhibited superoxide-scavenging activity in a dose-dependent manner. Egg-yolk protein hydrolysates also showed 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and hydroxyl radical-scavenging activity. At 0.5% of the hydrolysates, DPPH and hydroxyl radical-scavenging activities were 74.2% and 91.7%, respectively. In food model systems, egg-yolk protein hydrolysates effectively inhibited thiobarbituric acid reactive substances (TBARS) formation from ground beef and tuna homogenates. These results suggest that egg-yolk protein hydrolysates are good source of natural antioxidants.