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bioses, carbohydrates whose molecules consist of two monosaccharide groups. All disaccharides have a glycoside type of structure in which the hydrogen atom of a glycoside hydroxyl of one monosaccharide molecule is replaced by a group from another monosaccharide molecule bonded by a hemiacetal or alcohol hydroxyl. In the former case the disaccharides that form lack reducing properties, but in the second case they have them (I). The group of irreducible disaccharides includes trehalose (mycose, or fungus sugar), which consists of two glucose groups (II), and saccharose, which consists of glucose and fructose groups (III). The group of reducible disaccharides includes maltose (IV), cellobiose (V), and lactose (VI).

Disaccharides may contain the five- or six-membered rings of the monosaccharides (pentoses and hexoses) and may differ with respect to the configuration of the glycoside bond (α- or β-glycosides). The spatial forms (conformations) of the rings of the monosaccharide groups in the various disaccharides can vary. Thus, cellobiose and maltose differ not only in the configuration of the glycoside bond (α in maltose and β in cellobiose) but also in the fact that in cellobiose both groups have the same conformation, whereas in maltose they are different.

Disaccharides crystallize well, are readily soluble in water and 45-48-percent alcohol, only slightly soluble in 96-percent alcohol, optically active, and sweet to the taste. They are hydrolyzed by acids (in the case of saccharose it is called inversion); if the monosaccharide group has a five-membered ring the rate of acid hydrolysis of the disaccharide is increased. Disaccharides are also hydrolyzed by enzymes (carbohydrases), such as α- and β-glucosidases (depending on the type of glycoside bond in the disaccharide). Hydrolysis produces monosaccharides.

Disaccharides are widespread in animals and plants. They occur in the free state (as products of biosynthesis or of partial hydrolysis of polysaccharides) and in the form of structural components of glycosides and other compounds. Disaccharides are usually produced from natural sources— for example, saccharose from the sugar beet or from sugar-cane, and lactose from milk. Many disaccharides can be synthesized by chemical and biochemical means.

Saccharose, lactose, and maltose are valuable food and flavoring substances. The sugar industry produces saccharose.


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References in periodicals archive ?
Prebiotics are classified as disaccharides, oligosaccharides and polysaccharides and most commonly used prebiotics includes lactulose, mannan-oligosaccharide (MOS), inulin, soy Fructo-oligosaccharide(FOS) and galacto-oligosaccharide (GOS).
The suggested limits on intake of sugars in the draft guidelines apply to all monosaccharides (such as glucose and fructose) and disaccharides (such as sucrose or table sugar) that are added to food by the manufacturer, the cook or the consumer, as well as sugars that are naturally present in honey, syrups, fruit juices and fruit concentrates.
The WHO's limits on intake of sugars apply to all monosaccharides (such as glucose, fructose) and disaccharides (such as sucrose or table sugar).
12) Meanwhile, research had been taking place into a group of short chain carbohydrates poorly absorbed in the small intestine, commonly known as FODMaPs--an acronym for fermentable oligosaccharides, disaccharides, monosaccharides and polyols.
HYALURONIC ACID (HA)--also called hyaluronan or hyaluronate--is an anionic, nonsulfated polymer of disaccharides with a molecular formula of (C14H21N011)n.
Those are disaccharides, but there are also the monosaccharides like fructose and galactose," said Larry Brinkwell, the lab chemist.
6-8]) Consequently, some compounds such as polyols, polysaccharides, disaccharides, amino acids, proteins, vitamins, and various salts have been examined for their potential role to improve the survival of bacteria throughout freeze drying process [9-12, 13]) reported that lipid oxidation of membrane fatty acids were responsible for cell death during storage for Lactobacillus plantarum.
Kaden Biochemicals' rare sugar lines include monosaccharides, disaccharides and trisaccharides such as rhamnose, arabinose, and galactose.
20), an enzyme located in the small intestine epithelium, catalyzes the cleavage of disaccharides and oligosaccharides to glucose.
HS has structural domains consisting of segregated blocks of repeating GlcA-([beta]1-4)-GlcNAc disaccharides (NA domains), similar to the GlcA-([beta]1-3)-GalNAc/34 repeating unit in CS, and blocks of highly sulfated, heparin-like IdoA-([beta]1-4)-GlcNS disaccharides (NS domains).
Previous studies have shown that gametophytes that are grown in conditions closely resembling the fern's natural environment have higher levels of mono- and disaccharides than gametophytes or protonemal callus grown on agar medium (Abney, 2004).
They include monosaccharides (glucose, fructose, xylose or mannose), disaccharides (sucrose, lactose and maltose), trisaccharides, oligosaccharides and polysaccharides.