Food: Anything eaten to satisfy appetite and to meet physiology needs for growth, to maintain all body processes, and to supply energy to maintain body temperature and activity. Because foods differ markedly in the amount of the nutrients they contain, they are classified on the basis of their composition and the source from which they are derived.

Food Additives: Natural and synthetic compounds added to food to supply nutrients, to enhance color, flavor, or texture, and to prevent or delay spoilage. Since ancient times table salt has been a preservative for fish, ham, and bacon, and sugar has been used to preserve jelly, fruit jams, and fruit preserves. At present more than 2500 food additives of all kinds are known. The principal preservative compounds used today are benzoid acid, C6H5COOH, sodium benzoate, C6H5COONa, and calcium propionate, (C2H5COO)2Ca. Chlortetracycline and oxytetracycline are antibiotics used to delay spoilage of fresh fish and poultry.

Nutrients -mineral and vitamins- are added to foods to increase their nutritional value or to restore vitamins or minerals lost during processing. Vitamin D is added to milk, vitamin C to orange drink, and vitamin A to margarine. Vitamin C also used as an antioxidant for fresh fruits and frozen fish. Coloring agents, natural and synthetic flavorings, and flavor enhances such as monosodium glutamate are added to make food more appealing. More than 750 synthetic flavorings are known. Other additives sucha as agar and gelatin are used as texturizers or emulsifiers in foods such as ice cream and frozen desserts.