A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 and thus with the empirical formula Cm(H2O)n, which does not mean the H has covalent bonds with O. However, not all carbohydrates conform to this precise stoichiometric definition, nor are all chemicals that do conform to this definition automatically classified as carbohydrates.
A disaccharide is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common examples are sucrose, lactose, and maltose.
Glucose is a sugar with the molecular formula C6H12O6. Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight. Glucose is used by plants to make cellulose—the most abundant carbohydrate in the world—for use in cell walls, and by all living organisms to make adenosine triphosphate (ATP), which is used by the cell as energy.
Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amounts in staple foods such as wheat, potatoes, maize (corn), rice, and cassava (manioc).
Fructose, or fruit sugar, is a ketonic simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed by the gut directly into the blood of the portal vein during digestion. The liver then converts both fructose and galactose into glucose, so that dissolved glucose, known as blood sugar, is the only monosaccharide present in circulating blood.
Sorbitol, less commonly known as glucitol, is a sugar alcohol with a sweet taste which the human body metabolizes slowly. It can be obtained by reduction of glucose, which changes the converted aldehyde group (−CHO) to a primary alcohol group (−CH2OH). Most sorbitol is made from potato starch, but it is also found in nature, for example in apples, pears, peaches, and prunes. It is converted to fructose by sorbitol-6-phosphate 2-dehydrogenase. Sorbitol is an isomer of mannitol, another sugar alcohol; the two differ only in the orientation of the hydroxyl group on carbon 2. While similar, the two sugar alcohols have very different sources in nature, melting points, and uses.
A sugar substitute is a food additive that provides a sweetness like that of sugar while containing significantly less food energy than sugar-based sweeteners, making it a zero-calorie or low-calorie sweetener. Artificial sweeteners may be derived through manufacturing of plant extracts or processed by chemical synthesis. Sugar substitute products are commercially available in various forms, such as small pills, powders, and packets.
Xylitol is a chemical compound with the formula C
5H
12O
5, or HO(CH2)(CHOH)3(CH2)OH; specifically, one particular stereoisomer with that structural formula. It is a colorless or white crystalline solid that is freely soluble in water. It is classified as a polyalcohol and a sugar alcohol, specifically an alditol. The name derives from Ancient Greek: ξύλον, xyl[on] 'wood', with the suffix -itol used to denote it being a sugar alcohol.
Inverted sugar syrup, also called invert syrup, invert sugar, simple syrup, sugar syrup, sugar water, bar syrup, syrup USP, or sucrose inversion, is a syrup mixture of the monosaccharides glucose and fructose, that is made by hydrolytic saccharification of the disaccharide sucrose. This mixture's optical rotation is opposite to that of the original sugar, which is why it is called an invert sugar.
Sugar alcohols are organic compounds, typically derived from sugars, containing one hydroxyl group (−OH) attached to each carbon atom. They are white, water-soluble solids that can occur naturally or be produced industrially by hydrogenating sugars. Since they contain multiple (−OH) groups, they are classified as polyols.
Trehalose is a sugar consisting of two molecules of glucose. It is also known as mycose or tremalose. Some bacteria, fungi, plants and invertebrate animals synthesize it as a source of energy, and to survive freezing and lack of water.
Mannitol is a type of sugar alcohol used as a sweetener and medication. It is used as a low calorie sweetener as it is poorly absorbed by the intestines. As a medication, it is used to decrease pressure in the eyes, as in glaucoma, and to lower increased intracranial pressure. Medically, it is given by injection or inhalation. Effects typically begin within 15 minutes and last up to 8 hours.
Lactitol is a disaccharide sugar alcohol produced from lactose. It is used as a replacement bulk sweetener for low calorie foods with 30–40% of the sweetness of sucrose. It is also used medically as a laxative.
Maltitol is a sugar alcohol used as a sugar substitute and laxative. It has 75–90% of the sweetness of sucrose and nearly identical properties, except for browning. It is used to replace table sugar because it is half as calorific, does not promote tooth decay, and has a somewhat lesser effect on blood glucose. In chemical terms, maltitol is known as 4-O-α-glucopyranosyl-D-sorbitol. It is used in commercial products under trade names such as Lesys, Maltisweet and SweetPearl.
Isomaltulose is a disaccharide carbohydrate composed of glucose and fructose. It is naturally present in honey and sugarcane extracts and is also produced industrially from table sugar (sucrose) and used as a sugar alternative.
Hydrogenated starch hydrolysates (HSHs), also known as polyglycitol syrup, are mixtures of several sugar alcohols. Hydrogenated starch hydrolysates were developed by the Swedish company Lyckeby Starch in the 1960s. The HSH family of polyols is an approved food ingredient in Canada, Japan, and Australia. HSH sweeteners provide 40 to 90% sweetness relative to table sugar.
Glucose-galactose malabsorption is a rare condition in which the cells lining the intestine cannot take in the sugars glucose and galactose, which prevents proper digestion of these molecules and larger molecules made from them.
Isomaltooligosaccharide (IMO) is a mixture of short-chain carbohydrates which has a digestion-resistant property. IMO is found naturally in some foods, as well as being manufactured commercially. The raw material used for manufacturing IMO is starch, which is enzymatically converted into a mixture of isomaltooligosaccharides.
Trehalulose is a disaccharide made up of a molecule of fructose bound to a molecule of glucose. Like isomaltulose, it is a structural isomer of sucrose that is present in small quantities in honey. It makes up 50% of sugars in the honeydew of silverleaf whiteflies and is synthesised from sucrose by some bacteria, such as Protaminombacter rubrum. Because the anomeric carbon of the fructose moiety is not involved in the glycosidic bond, it is a reducing sugar.
