An acidic oil-in-water-type emulsified food comprising an egg white hydrolyzate. A method of producing the acidic oil-in-water-type emulsified food comprising emulsifying an aqueous phase component and an oil phase component in the presence of the egg white hydrolyzate. An antioxidant comprising an egg white hydrolyzate obtained by treating egg white with a neutral protease originating from a microorganism belonging to the genus Aspergillus. A flavor improving agent comprising an egg white hydrolyzate obtained by treating egg white with a neutral protease originating from a microorganism belonging to the genus Aspergillus.