In this role,irradiation offers an alternative to chemicals for use with potatoes,tropical and citrus fruits,grains,spices,and seasonings.However , since no residue is left in the food,irradiation does not protect against reinfestation as insect sprays and fumigants do. Food irradiated at this level are not sterile;therefore they must be properly refrigerated,handled,and cooked the same as non-irradiated foods.