At the same time that cooking develops the characteristic flavors of meat, it also promotes chemical changes that lead to characteristic, stale, cardboard-like “warmed-over flavors” when the meat is stored and reheated. (Complex or strongly flavored dishes may actually improve with time and reheating; warmed-over flavor develops within the meat itself.) The principal source of off-flavors is unsaturated fatty acids, which are damaged by oxygen and iron from myoglobin. This damage occurs slowly in the refrigerator and more rapidly during reheating. Meats with a greater proportion of unsaturated fat in their fat tissue—poultry and pork—are more susceptible to warmed-over flavor than beef and lamb. Cured meats suffer less because their nitrite acts as an antioxidant.