Carbohydrate definition and food sources

With the energy value of 4 calories, carbohydrates are one of the most basic nutrients in foods. They are indispensible in foods by virtues of their role as sweeteners, thickening, bulking and gelling agents.

Carbohydrates are composed of three elements: carbon, hydrogen and oxygen. The word carbohydrate was originally derived from the fact that the greater part of the compound in this class had the empirical formula Cn(H2O)n. The values of n range from three to many thousands. The number and arrangement of these elements in the carbohydrate molecule differentiate one carbohydrate from another.

This formula now considered too restrictive and a more useful definition might be ‘polyhydroxy aldehydes or ketones and their derivatives’. This later definitions encompass deoxy sugars, sugar alcohols, sugar acids, amino sugars.

Plants are the primary sources of carbohydrates in the human diet. Carbohydrates occur in fruits and vegetables as storage reserves in seeds, roots, and tubers; in the sap; and as constituents of the structural tissues, they are also found in the milk, blood, and tissues of animals.

Carbohydrate should make up about 5/7 of the solid part of the diet and ideally no more than 2/7 of the carbohydrates should be refined sugars such as glucose.
Carbohydrate definition and food sources 

Oligosaccharide in foods

Complex carbohydrates consist of many monosaccharides bonded together in a variety of bonding patterns. 

Oligosaccharides yield 3 to 6 monosaccharide units on hydrolysis. These carbohydrates are attached to either the side chain oxygen atom of serine or threonine residues by O-glycosidic linkages or to the side chain nitrogen of asparagine residues by N-glycosidic linkages.

The commonly found oligosaccharides in foods are sucrose, maltose, lactose, raffinose and stachyose. 

Sucrose found throughout the plant world is most abundant in sugarcane, sugar beet and maple syrup. It is the familiar table sugar.

Foods high in oligosaccharides include onions, chicory, Jerusalem artichoke, asparagus globe artichoke, leek, garlic banana, and wheat.

Oligosaccharides also present in dried beans, soybeans, peas and lentils. Oligosaccharides have been dietary staples since antiquity and have received mush less attention than other carbohydrates, including simple sugars or dietary fiber.

In the body, oligosaccharides are components of cell membranes allowing cells to recognized and interact with one another.

Oligosaccharides play a key role in processes that take place in the surfaces of cells, particularly in cell-cell interactions and immune recognition.

Lately, interest in oligosaccharides has increased duetheir functional properties. These induce sweetening, ability, fat replacement, and enhancement of a ‘healthy’ gastrointestinal tract.
Oligosaccharide in foods