The invention provides a deterioration inhibitor with an even stronger effect than the prior art against deterioration of flavors and fragrances in foods and beverages or cosmetics, which is attributed to heat, light and the like, and especially against production of deterioration odors derived from citral.It is a food flavor deterioration inhibiting material comprising as an effective component a product obtained by treatment of a tea extract component with an oxidizing 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.