579687 Disclosed is a skin-whitening agent comprising, as an effective ingredient, a whey protein hydrolyzate having the following characteristics: (A) the molecular weight is distributed within 10 kDa with a main peak of 200 Da to 3 kDa； (B) the APL (average peptide-chain length) is 2 to 8； (C) the free amino acid content is 20% or less； and (D) the antigenicity is one-ten thousandth of antigencity of ?-lactoglobulin or less, wherein the whey protein hydrolyzate contained as the effective ingredient is obtained by enzymatically decomposing a whey protein while thermally denaturing the whey protein using a heat-resistant protein hydrolyzing enzyme under pH 6 to 10 at 50 to 70°C, then heating the obtained product and thereby deactivating the enzyme, and then concentrating the obtained product by using ultrafiltration (UF) membranes with a molecular weight cut off in a range of 1 kDa to 20 kDa. Further disclosed is the use of a whey protein hydrolyzate in the manufacture of a skin-whitening agent in the treatment of age spots and/or freckles, said whey protein hydrolyzate having the following characteristics: (A) the molecular weight is distributed within 10 kDa with a main peak of 200 Da to 3 kDa； (B) the APL (average peptide-chain length) is 2 to 8； (C) the free amino acid content is 20% or less； (D) the antigenicity is one-ten thousandth of antigenicity of b-lactoglobulin or less； and (E) the whey protein hydrolyzate is concentrated by using ultrafiltration (UF) membranes with a molecular weight cut off in a range of 1 kDa to 20 kDa.
