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Carbohydrates

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The carbohydrate family includes a variety of chemicals.  It has always been an important part of human diet.  Carbohydrates not only act as a source of energy, they also have other physiological influences, some of which are beneficial but others undesired.  Structurally carbohydrates can be categorized into mono-, di-, oligo-, and polysaccharides.  Dietary fiber, another critical dietary component, also consists of certain oligo- and polysaccharides, which are not digested in the human small intestine by the endogenous enzymes. 

Monosaccharides – The simplest sugars, such as glucose, galactose, and fructose.  They provide a sweet taste in foods and are readily converted to energy via quick absorption into the bloodstream.

Disaccharides – Two molecules of monosaccharides undergo condensation to form various disaccharides.  The most common ones are sucrose (Glucose-Fructose), maltose (Glucose-Glucose), and lactose (Galactose-Glucose).  Similar to monosaccharides, most of them can be readily utilized to provide energy after specific endogenous enzymes convert them to their corresponding monosaccharides.

Oligosaccharides – Made up of three to approximately ten monomeric saccharide units.  Examples are raffinose  (Galactose-Glucose-Fructose) and stachyose (Galactose-Galactose-Glucose-Fructose). More complex oligosaccharides include fructooligosaccharides (FOS), galactooligosaccharides (GOS), and etc.  Codex Alimentarius Commission has defined non-digestible oligosaccharides as a part of dietary fiber. 

Polysaccharides – Long chains of monosaccharides (usually >>10).  This category includes starch (consisting of amylose and amylopectin), xylan, mannan, cellulose, hemicellulose, pectin, and chitin.