The invention provides a deterioration inhibitor containing an amount of a product obtained by treatment of a tea extract with an oxidizing enzyme and then inactivating the enzyme. Addition of a deterioration inhibiting material according to the invention to a food or beverage or a cosmetic can inhibit deterioration of flavor and fragrance, with use in smaller amounts than conventional deterioration inhibitors. A particularly notable effect is exhibited against production of p-cresol and p-methylacetophenone which are citral-derived deterioration odor components, and therefore it is suitable for foods and beverages or cosmetics with citral-containing citrus-like flavors and fragrances.
