Dextrins changes

STADEX Dextrins are partially hydrolyzed starches that are prepared by heating or dry roasting starch in the presence of an acid catalyst. The conversion process - the change from starch to dextrin - changes the properties of the parent starch in several ways. Notably, the dextrin exhibits a thinner cooked-paste viscosity, an increased cold water solubility, and a color change from white to off-white or yellow. 

McClenahan, Tilden and Hudson pointed out that the ratio of a to /3 dextrin changed during the enzymolysis of starch, and further that it was possible to increase the yield of /3-dextrin to over 50 % of the weight of the starch used by adding a dextrin precipitant during the enzymolysis. Similar results were obtained by French and coworkers. ... 

The acid hydrolysis of starch granules from potato, waxy maize, and amylo-maize-7 was studied in different ratios of mixtures of two of the four alcohols, from 100/0 to 0/100% in 10% (v/v) intervals [53]. Again, a series of soluble limit dextrins was obtained in 48-72 hr of reaction. The average d.p. of the limit dextrins decreased as the content of the higher alcohol was increased. Plots of the d.p. of the limit dextrins vs. the ratio of each alcohol mixture produced curves that resembled titration curves, with different plateau regions in which the d.p. of the limit dextrins changed very slowly or not at all. These plateau regions were characteristic and dependent on the types of alcohols, the volume ratios of the two alcohols in the mixture, and the type of starch. It was proposed that the formation of... 

While nature uses coenzyme-dependent enzymes to influence the inherent reactivity of the coenzyme, in principle, any chemical microenvironment could modulate the chemical properties of coenzymes to achieve novel functional properties. In some cases even simple changes in solvent, pH, and ionic strength can alter the coenzyme reactivity. Early attempts to present coenzymes with a more complex chemical environment focused on incorporating coenzymes into small molecule scaffolds or synthetic host molecules such as cyclophanes and cyclo-dextrins [1,2]. While some notable successes have been reported, these strategies have been less successful for constructing more complex coenzyme microenvironments and have suffered from difficulties in readily manipulating the structure of the coenzyme microenvironment. 

Molecular cavities are of topical research interest because of their ability to enclose and bind guest molecules. They may serve as models for the study of binding sites between, e.g. drugs, odorant/taste substances, antigens, etc. and receptors. Cyclo-dextrins, as prime examples of host cavities, have found many useful applications. This is due to the guest molecules being bound within the cavity which changes properties such as solubility, volatility and reactivity. 

Dextrin is a hydrolysis product intermediate betw starches and sugars, such as dextrose (see next item). It does not give the blue iodine reaction of starch and is not fermentable, but is changed to maltose by the action of enzymes (diastase) and to dextrose by the action of acids... 

Table IV. Changes of the flavor content of cyclo-dextrin spice complexes after ten years storage under nonnal conditions...

The change is at first into dextrin—see Starch—then sugar was diminished by it. If they used it as acid, as ... 

Figure 3. Change in the relative hydrolysis rates (based on sulfuric acid) of dextrin with the mole ratio of vinyl alcohol to vinylsulfonic acid repeating units at 80°C, keeping the concentration of vinulsulfonic acid unit constant at 5.00 X I0"3N. (O) In the presence of the random copoly (vinyl alcohol-vinylsulfonic acid) (%) in the presence of poly (vinyl alcohol)-poly(vinylsulfonic acid) mixture. [Substrate] = 2.00 X 10"2M.

Incomplete coverage of the surface of such a fifth-generation POPAM dendrimer exposes hydrophobic areas of adamantyl units remaining uncomplexed by cyclodextrins on the dendritic outer shell [38]. Pyrenes were used as neutral fluorescence probes to examine whether this might lead to aggregation in water driven by the hydrophobic effect [39a]. Their inclusion in the dendrimer/cyclo-dextrin aggregate leads to changes in fluorescence intensity and in the vibrational fine structure. Formation of excimers was also observed. 

Figure 4 Change in IOP of normotensive rabbits treated with 0.1% dexamethasone (Dex), 0.1% loteprednol etabonate (LE), and vehicle (50% w/w 2-hydroxypropyl- 3-cyclo-dextrin water solution). Twelve rabbits were investigated in crossover experiments drugs were administered in one eye (100 pL) every hour during the 8-h periods marked on the graph. (Data from Ref. 43 represent mean SE both for treated (T) and control (C) eyes.)...

Figure 24. Dimensional representation of phosphorylase limit dextrin structure and changes produced by action of the debranching enzyme...

Samec3,5 has conducted comparative studies on the effects of various types of radiation on the properties of the dextrins produced and found notable differences. The origin of the starch seems to be a factor of minor importance, at least upon sonication with 995 kc/s and 120 W. Potato and arrowroot starch gave similar results.309 The action of ultrasound on starch gels produces complex changes.312,313 The mechanism of disintegration has been discussed by Sozaburo.314... 

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