Food additives are substances that are added to a food during processing. They may be from natural sources (i.e. salt) or synthetic (man made). They are used to help maintain or enhance the flavor, texture, appearance, or nutritional value of a food, and extend shelf life. They are also used to prevent a packaged and processed food from spoiling and to keep a food blended, thickened, or moist until they are eaten. Often nutrients are added (enriched) to replace those lost during processing or to fortify a food because the general population is usually deficient in these nutrients.