Carbohydrates BT - Principles of Food Chemistry

Abstract

Carbohydrates or saccharides (from the Greek word sakkharon meaning sugar) occur in plant and animal tissues as well as in microorganisms; as macronutrients they are the human body’s preferred energy source, providing fuel for the central nervous system and energy for working muscles. Carbohydrates also serve as (1) a short-term energy source for all organisms, (2) structural molecules in plants, and (3) storage forms of foods in plants and animals. Carbohydrates are technically hydrates of carbon with the empirical formula Cm(H2O)n (where m could be different from n), but structurally they are more accurately viewed as polyhydroxy aldehydes and ketones. Carbohydrates can be divided into three chemical groups: monosaccharides, oligosaccharides, and polysaccharides, with the first being small (lower molecular weight) and commonly referred to as simple sugars. Carbohydrates in food can also be classified as simple or complex, with the difference between the two forms being the chemical structure and how quickly they are absorbed and digested. In animal organisms, the main sugar is glucose and the storage carbohydrate is glycogen; in milk, the main sugar is almost exclusively the disaccharide lactose. In plant organisms, a wide variety of monosaccharides and oligosaccharides occur, as well as storage polysaccharides such as starch, and structural polysaccharides such as cellulose and hemicellulose. Gums are a varied group of polysaccharides obtained from plants, seaweeds, and microorganisms. Because of their useful physical properties, the gums have found widespread application in food processing. The main carbohydrates that occur in a number of example food products are listed in Table 4.1.