Dextrins

DEXTRINS (C₆H₁₀O₅)_n, a mixture of polysaccharides that are intermediate products in the enzymatic or acidic hydrolysis of starch or glycogen. Dextrins are dextrorotatory, amorphous, white powders, easily soluble in water to form viscous, sticky solutions; some possess reducing properties; they are not capable of fermentation. The end product of hydrolysis is maltose, resp. glucose. Four types of dextrins formed under the influence of diastase are distinguished: 1) amylodextrins, which give a blue coloration with iodine, 2) erythrodextrins—a reddish-brown coloration with iodine, 3) achrodextrins, which do not color with iodine, as well as 4) maltodextrins. The degree of association of molecules decreases from the 1st to the 4th type of dextrin, while solubility in alcohol increases. Dextrins are also formed when starch is heated to 180-200° (dark technical dextrin) or when starch moistened with HNO₃ is dried at 110°. Dextrin-like substances are also formed by the action of mineral acids on D-glucose (reverse synthesis). When starch or glycogen is acted upon by Bacillus macerans, crystalline dextrin-polyamyloses are formed (Schardinger, Pringsheim): α- and β-hexa-amyloses [(C₆H₁₀O₅)₂]₃ and [(C₆H₁₀O₅)₃]₂. α-tetraamylose [(C₆H₁₀O₅)₂]₂. Their structure is not fully elucidated. Dextrins are found in the intestine; they have been detected in the blood of the portal vein after carbohydrate food (Otto and Mering). Once found in the urine of a dog (Kotake). Apparently, a dextrin-like substance is also contained in normal human urine. Dextrins are also contained in the seeds of some plants. Dextrins are used in technology as glue, a thickener in dyeing fabrics, etc. When baking bread, the starch of flour turns into dextrins, soluble in water and more easily assimilated by the body.