Abstract
The effects of heat on the antioxidative activity of ovalbumin toward linoleic acid (LA) in an emulsion were studied. After ovalbumin had been heated at 80°C or more, both the antioxidative activity and superoxide radical scavenging activity were markedly elevated. Heating at this temperature rendered the sulfhydryl residues of ovalbumin more reactive to 5, 5-dithiobis-(2-nitrobenzoic acid) and more susceptible to oxidation during incubation with LA in an emulsion. Among the amino acids tested, methionine, histidine, and cysteine acted as antioxidants in an emulsion, and cysteine and histidine acted as superoxide radical scavengers. Both the hydrophobicity and fat-binding capacity were markedly increased after ovalbumin had been heated at 80°C or more. Heating ovalbumin might have increased its antioxidative activity by exposing antioxidative amino acid residues like cysteine and histidine and by enhanced masking of the surface of oil droplets, providing a suitable environment for the antioxidative activity of the amino acid residues.
