Maltose

MALTOSE (malt sugar, C₁₂H₂₂O₁₁), a disaccharide built from d-glucose residues according to the following monoglycosidic linkage type: α < 1,5 > glycosido - 4 < 1,5 > glucose (see Disaccharides). Maltose is an intermediate product of the acid hydrolysis of glycogen and starch, and the final product of their hydrolysis under the influence of amylases; therefore, it is found in the digestive tract and is an intermediate product in distilling and brewing. Maltose is found in some plants. Maltose crystallizes with 1 molecule of water in the form of fine needles. It rotates the plane of polarized light strongly to the right [d]_D - about +138°; it exhibits the phenomenon of mutarotation. Maltose is easily soluble in water, fairly easily in alcohol, and insoluble in ether. Its reducing power is less than that of glucose (0.0074 g of maltose reduces 1 cm³ of Fehling's solution). Maltose phenylosazone precipitates only upon cooling of the liquid, which has been heated for 1½ hours in a boiling water bath; unlike glucose phenylosazone, it is soluble in a mixture of equal parts of acetone and water and is cleaved by yeast. Maltose is fermented by yeast. Under the influence of maltase, as well as when boiled with acids, maltose is cleaved to form glucose. Under the influence of alkalis, browning and cleavage occur with the formation of glucose, which partially converts into fructose and mannose, lactic acid, etc. Maltose is formed from glucose under the influence of emulsin (Frankland, Armstrong) and yeast maltase (Pringsheim, Leibowitz). Maltose is a strong glycogen former. The detection of maltose is mainly based on the significant difference in the results obtained in its quantitative determination by polarimetry and by titration calculated as glucose, on the properties of its osazone, and on its ability to ferment. Maltose is the main constituent of malt extract (66%), nutritional mixtures (Keller's food), Liebig's soup, etc. Isomaltose. This term refers to products of very different origins: a disaccharide obtained as a result of the reversible action of mineral acids on glucose (E. Fischer's isomaltose), Armstrong's revertose, formed by the action of maltase on glucose, Ling's isomaltose, formed by the action of amylase on amylopectin or on α,β-hexaamylose (see Starch), and others. Pringsheim and some other authors deny the existence of isomaltose. According to some authors (Baisch, Lemaire, Pavy), isomaltose is found in small quantities in normal urine, blood, and muscles.