For example, deoxyribose contains 5 carbon atoms, 10 hydrogen, but only 4 oxygen rather than 5 as is customary for pentose. Moreover, some compounds that are properly classified as carbohydrates in terms of chemical properties contain nitrogen or sulfur addition to carbon, hydrogen, and oxygen.
Carbohydrate biosynthesis in plants starting from carbon disaccharide and water with the help of light energy i.e. photosynthesis is the basis for the existence of all other organisms which depend on the intake of organic substance with food.
The major carbohydrate containing foods in the human diet are: cereal, sweeteners, root crops, pulses, vegetables, fruit, and milk products. Carbohydrates play a major role in human diets, comprising some 40-75% of energy intake. Their nutritional energy value amounts to 17 kJ/g or kcal/g. Their most important nutritional property is digestibility in the small intestine.
Carbohydrates can be classified based on their chemical structure and/or based on their physiological effects. There are three main groups, monosaccharide, or simple sugars; oligosaccharides, of which the most prevalent in nature are the disaccharides; and polysaccharides the most complex of the carbohydrates.
Defining carbohydrates by chemical structure, does not take into account their physiological differing response, such as differences in satiety value, gastric emptying times and effects on glucose and insulin levels.
Starch is by far the most important source of carbohydrates in the human diet amounting to approximately 50% of total carbohydrate in the United States, but often as much as 75% total carbohydrates in some of the developing countries.
Many starches do not have the functional properties needed to impart or maintain desired qualities on food products. As a result, some starches have been modified to obtain the functional properties required. These type modified starches, also known as derivates.
Sucrose ranks next in important comprising about 25% of carbohydrates intake. In the last 70 years the intake of complex carbohydrates in the diet of United States has decreased, and the intake of sucrose has markedly increased.
Carbohydrate group of food
