Dextrin linear, chemical structure

Optical rotation and refractometric detectors were combined to characterize a series of dextrins by gel permeation chromatography and high performance liquid chromatography (HPLC). Gel permeation fractionates according to the hydrodynamic volume when adsorption is avoided/ and for this reason separates isomaltodextrins from linear maltodextrins. Specific rotation power [a] is directly obtained and confirms the chemical structure. Elution of cyclodextrins is also tested and discussed. HPLC reverse phase chromatography separates the anomers as shown by optical rotation and allows good resolution in the range of low DP. 

Based on the experimental data on vinylidene chloride pofynerization in the presence of linear dextrin, a chemical interaction between poly(vinylidene chloride) and p-cyclodextrin was ruled out The results of the experiments demonstrated an absence of a chain transfer to linear dextrin, i.e. an absence of chemical bonds. In addition, comparing the data of investigation of the structure of obtained compounds indicated a nonchemical bonding of p-cyclodextrin and poly(vinylidene chloride). Due to the identity of the crystalline structure of monomeric adducts of P-cyclodextrin with both MMA and vinylidene chloride, on the one hand, and to the formation of an unstable product by a solid-state polyn rization of p-cyclodextrin with MMA (dissociates into P-cyclodextrin and PMMA on being treated with hot water), on the other hand, these researchers also assumed an absence of chemical bonds in the stable product, obtained in the same way and consisting of poly(vinylidene chloride) and p-cyclodextrin. 

FIGURE 3.3 Chemical structure of the main soluble sugars found in cereal grains, (a) Glucose, (b) Fructose, (c) Sucrose, (d) Maltose, (e) Maltotriose. (f) Linear dextrin, (g) Branched dextrin. 

Further chemical changes that occur during dextrinization should be discussed separately for the case of formation of British gum, and for variously catalyzed thermal processes. Thus, when starch (1) is heated in the presence of moisture, random hydrolytic scission at the (1 - 6), and more readily at the (1 — 4), linkages has been proposed to occur in the branched chains of amylopectin, to give more-linear structures, leading to the observed decrease in viscosity. o-Glucosyl oxocarbonium ions (2) were postulated as intermediates, but free radicals (3) formed by homolytic fission at the (1 4)-glycosidic bond are also feasible. 

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