DEXTRINS

From Big Medical Encyclopedia

DEXTRINS (C 6 H 10 O 5 ) x - products of partial splitting of polysaccharides: starch, dextran and glycogen of an animal and plant origin. In comparison with these polysaccharides (see) D. have higher comprehensibility. E.g., at bread baking starch of flour passes into D., water soluble and easier acquired by an organism.

Are found in intestines, and also found in blood of a portal vein of animals and the person after acceptance of food, carbohydrate-rich. In the insignificant number of D. contain in urine.

At hereditary defect of enzyme a dextrin (amyl) - 1,6 glucosidases (KF 3.2.1.33) develop the disease which is characterized by abnormal accumulation of a glycogen in a liver and a cardiac muscle — the so-called (limit-dekstrinoz), or Forbes's disease limited dextrinases (a glycogenosis of the III type according to Cory). Some D. are applied to diagnosis of the hereditary diseases connected with insufficiency of glucosidases (see). E.g., biochemical, the diagnosis of a number of disakharidoz (see. Disaccharides ) it can be put during the use as certain D.' substrate instead of hardly accessible disaccharides like isomaltose. Shardingerovsky D. apply at differential diagnosis the limited dextrinase (a glycogenosis of the III type).

Apply in paper, textile, match, printing and other industries of hl. obr. as adhesive substances. The best on the properties is the dekstrinovy glue received from corn starch.

D.'s education from polysaccharides is carried out by means of heat treatment, acid hydrolysis, and also under the influence of various enzymes splitting polysaccharides of type starch (see) and glycogen (see): alpha, beta and gamma amylases and glikogenfosforilaza (KF 2.4.1.1). At the same time also gamma dextrins are formed respectively alfa1-, beta.

Properties D. are substantially caused their pier. it is powerful (weight), depending on depth of disintegration of initial polysaccharide. So, in process of decrease of size of the molecules D. which are formed at an alpha amylolysis of starch their reducing power, solubility in alcohol increases, the size of specific rotation decreases. Coloring by their iodine changes from blue-violet to red-brown, orange and yellow. The received D. depending on coloring by iodine and solubilities in alcohol carry names of amilodekstrin, erythrodextrins, achrodextrins and maltodextrins. In total D. easily rastvorima in water.

The final alpha dextrins received from branched polysaccharides — amylopectin and a glycogen, represent the oligosaccharides consisting of a small number of glucose units. On the contrary, final beta and F-dextrins are characterized by a high polymerization degree. Their pier. weight makes usually not less than 35 — 50% a pier. weight of initial polysaccharides.

As a result of action on starch of the alpha amylases formed by cultures you. macerans, turn out D. called alpha and Shardinger's beta dextrins or cycloamyloses. These are the crystal substances representing the chains closed in a ring from five or six glucose units connected among themselves alpha 1,4 - a glucosidic bond. Shardinger's alpha Dextrins with iodine form needles of green color, Shardinger's beta dextrins — brown prisms. Shardinger's dextrins differ in low reducing power.

Dextrinization of starch is made for the technical purposes usually by heating to 110 ° after pretreatment salt or nitric to - that or during the heating to 180 — 190 ° during 5 — 6 hours without addition to - you.

See also Glycogenoses .


Bibliography: Kerr R. V. Chemistry and technology of starch, the lane with English, page 288, etc., M., 1956; Stepanenko B. N. Carbohydrates, progress in studying of a structure and metabolism, M., 1968; Pigman W. W. a. G about-e r r R. M of Chemistry of carbohydrates, N. Y., 1948; Radley J. A. Starch and its derivatives, L., 1968.

E. L. Rosenfeld.

Яндекс.Метрика