CARBOHYDRATES

Carbohydrates are one of the major groups of biological molecules made up from carbon, oxygen, and hydrogen.  They differ from fats (made from the same elements) in that the hydrogen and oxygen are in the same proportions as in water. Carbohydrates are divided, into the following four groups according to the number of saccharides (sugar molecules) they contain:

Saccharide is scientific name for sugar.

Monosaccharide is the scientific name for a sugar made from a single molecule. The most common monosaccharides are glucose, fructose, and galactose.

Disaccharide is the scientific name for a sugar made from two molecules of sugar. The most common disaccharides are sucrose (table sugar), maltose, and lactose.

Oligosaccharide is a polymer containing three to nine monosaccharides. A polymer (from Greek poly=many + mer=parts) is a large molecule (macromolecule), composed of many repeated subunits.

Polysaccharide is a polymer in which the single units of sugar unite into linear chains or branches. Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose, hemicellulose, and lignin.

ORIGIN OF CARBOHYDRATES

Photosynthesis is the process by which the chlorophyll-containing cells in green plants by the help of sunlight synthesise carbohydrates from carbon dioxide and water, with the simultaneous release of oxygen. This is the primary source of all food in the kingdoms of nature.

Chlorophyll is the green pigment found in plants that traps energy from sunlight for use in photosynthesis.

STRUCTURAL/INDIGESTIBLE CARBOHYDRATES

Dietary fibre is the indigestible portion of plant foods. Chemically, it consists of non-starch polysaccharides such as cellulose, hemicellulose, lignin, waxes, and many other indigestible plant components.

Bran is the hard outer layer of cereals. It should not be confused with chaff, which is coarser scaly material surrounding the grain, but not forming part of the grain itself. Bran is particularly rich in dietary fibre and contains significant quantities of starch, protein, vitamins, minerals, essential fatty acids and phytic acid.

Cellulose is a type of polysaccharide consisting of a linear chain of several hundred to over ten thousand glucose units. Cellulose is the structural component of the primary cell wall of green plants. Cellulose is the most common organic compound on Earth. About 33% of all plant matter is cellulose (e.g. wood consist of 40–50% cellulose).

Hemicellulose is a type of polysaccharide, present along with cellulose in almost all plants. While cellulose is crystalline, strong, and resistant to degradation by water, hemicellulose has a random, amorphous structure with little strength.

Lignin is a type of polysaccharide, present in the fibrous parts of plants and some algae. It is one of the most abundant organic substances, exceeded only by cellulose, and constituting from a quarter to a third of the dry mass of wood.

EDIBLE COMPLEX CARBOHYDRATES

Starch is a polysaccharide consisting of a large number of glucose units. It is produced by all green plants. It is the most common carbohydrate in the human diet and is c ontained in large amounts in such staple foods as grains, potatoes, cassava, sweet potato, beans, etc.

Fructo-oligosaccharides (from the group of oligosaccharides) consist of short chains of fructose molecules. They can be found in many vegetables.

SIMPLE CARBOHYDRATES/SUGARS

Simple sugars (or simple carbohydrates) are carbohydrates that are made up of only one or two units of sugar and are thus easily absorbed by the body.

Sucrose [C₁₂H₂₂O₁₁] or table sugar is a disaccharide, composed of one unit of glucose and one unit of fructose. Sucrose is the only component of white sugar and the main component of other types of sugars made from sugar cane and sugar beet.

Maltose (or malt sugar) is a disaccharide formed from two units of glucose. Maltose is produced when amylase breaks down starch. It is found in germinating seeds such as barley as they break down their starch.  

Lactose is a disaccharide derived from galactose (see below) and glucose that is found in milk. Lactose makes up around 2–8% of milk by weight, although the amount varies among species. 

Glucose is a monosaccharide which is the main component of starches in the grains, potatoes, etc. It is one of the two main ingredients of sucrose (see above). Glucose is also present in the blood where it is the main source of energy for body cells. For that reason it is called blood sugar.

Fructose (or fruit sugar) is a monosaccharide mainly found in fruits and other parts of the plants. It is one of the two main ingredients of sucrose (see above).

Galactose is a monosaccharide mainly found in dairy products.

Glyconutrients is the term applied to a specific group of eight simple sugars which are, according to some scientists, regarded as essential for the multitude of metabolic processes in the human body. These glyconutrients are contained in specific types of food, but they are mainly sold in the form of supplements.

NATURAL SWEETENERS

Jaggery is a traditional sugar consumed in Asia and Africa. It is a concentrated product of date, cane juice, or palm sap without removal of the molasses, and can vary from golden brown to dark brown in colour.

Molasses (American) or treacle (British) is a viscous by-product of the refining of sugarcane, grapes, or sugar beets into sugar.

ARTIFICIAL SWEETENERS

High fructose corn syrup (HFCS) is produced by milling maize to produce maize starch, then processing that starch to yield maize syrup, which is almost entirely glucose, and then adding enzymes (of unknown origin) which catalyze the transformation of some of the glucose into fructose. The result is an artificially made sweetener with a higher degree of sweetness, used in soft drinks and many other fast food products.

Saccharine is an artificial sweetener made from coal tar which belongs to the group of hydrocarbons.

Sucralose is produced synthetically from sucrose when three chlorine atoms replace three pairs of oxygen and hydrogen.