Maize starch, dextrinization

Results of Column Chromatography of Hydrolyzate of Methylated, Maize-Starch Dextrin ... 

The only example of this technique applied to the amylose component is that already described, of the action of Z-enzyme on the /3-limit dextrin. In the case of amylopectin, enzymic methods enable a distinction to be made between the proposed laminated and highly ramified structures (I and III, in Fig. 1, page 352). The method used by Peat and coworkers101 involves the successive action of /3-amylase and R-enzyme on waxy maize starch. /3-Amylolysis will degrade A-chains down to two or three units from the 6 —> 1-a-D interchain linkages. These latter linkages will protect the... 

When the / -limit dextrin of waxy-maize starch reacted with exo-maltohexahydrolase (EC 3.2.1.98), which can by-pass some a-(l- 6) linkages, the branched a-D-gluco-oligosaccharides expected, namely, 64-a-maltosylmaltopentaose (102), 63-a-maltotriosylmaltotetraose (103), 64-a-maltosylmaltohexaose (104), and 63-a-maltotriosylmaltopentaose... 

This results from the transformation of starch by means of heat or by the action of dilute acid or diastase. It is prepared principally from potato, wheat or maize starch and rarely from rice or other exotic starches. Many varieties of dextrin, made in diverse ways, are sold under different names. It occurs as a fine powder, either wliite, dirty white, yellowish or light brown as granules, similar in appearance to gum arabic and as a thick syrup, more or less highly coloured and opaque. In general dextrin has a special odour and taste, which are particularly marked in the pulverulent varieties. It is soluble in water, but insoluble in alcohol. Its solution is strongly dextro-rotatory the value of [a]D varies from 173° to 2250,but is mostly about 200°. With iodine different dextrins give bluish violet to brownish red colorations (the colour is observed by adding the iodine solution drop by drop if the mass is mixed after the first drops are added, the colour disappears). 

The best dextrins, derived from good potato starch, exhibit a shining reflection, those which appear opaque being usually obtained from wheat or maize starch. 

The doubly branched dextrins, 64,66-di-a-D-glucopyranosylmaltohexaose and 63,65-di -a-D-glucopyranosylmaltopentaose, isolated by Kainuma and French17 after action of porcine pancreatic a-amylase on waxy maize starch, established that the a-(l—>-6) branch linkages could be as close as having one glucosyl unit between them. No saccharides were found that indicated that the branch linkages could be adjacent to each other. 

Candy coatings are applied via repeated, successive application of dextrin and sugar solutions, followed by drying. Dextrins and monosubstituted starch hydrolyzates are used in candy coatings because of their clear, appetizing films. In this application, clarity, sheen and reduced cracking are desired. Oxidized waxy maize starches are also used.12 Starch used as an impressionable bed for casting candies is typically dent com starch with several tenths of a percent of mineral oil. The oil causes the starch to retain the imprinted shape for a more precisely formed candy piece. 

Another common method for determination of alpha-samylase involves measurement of the diminution of the iodine-stainability of whole starch or amylopectin )8-limit dextrin. These methods are useful, as very small quantities of alpha-amylase may be estimated in this way. They are comparative, and cannot be used to determine rates of bond scission, unless they are carefully calibrated by a method that measures reducing end-groups. Such a calibration has been made for the action of hog-pancreas alpha-amylase on waxy-maize starch, although the validity of the reducing-power determinations, made with iodine and thiosulfate, has been confirmed for maltose only thus, it is not yet known whether the calibration is actually valid for the experimental system in which larger oligomers, for example, the triose and tetraose, are also formed. 

The specific rotation,, of the products of dextrinization is randomly estimated. This index is not of any special interest. As reported for a maize starch, [a] (and its variation) is nonuniformly dependent on the temperature of dextrinization. After a given time of heating, it increases together with temperature ofdextrinization (from about +160° at 120°Cto+198° at 230°C). Only dextrinization at 210°C causes a drastic decrease of [aJo as a function of the time of dextrinization in other cases, the variation of this index is small. The decrease of [a]o is interpreted as the result of the formation of new yS-D bonds by D-glucosyl residues. 

Fig. 22.— Relationship between Amylolytic Index, Reducing Sugars, and Solubility of Dextrin, and Time of Dextrinization of Maize Starch in the Process Involving Alum. [Curves from 1 to 5 correspond to temperatures of the process which decrease regularly from 180 to 140 ° in decimal ranges, respectively.]...

Smith and coworkers - have subjected starch dextrins to the classical techniques of structural carbohydrate chemistry. In one study, four commercial maize-dextrins were fractionated from aqueous ethanol to obtain a sub-fraction which was the most resistant to periodate oxidation. This material was then methylated, the product hydrolyzed, and the resulting methylated sugars analyzed by column chromatography. Table II shows the results. The complexity of the dextrin structure is shown by the fact that only components 1, 2, and 5 arise in any large proportion from the methylation of maize starch. It is of interest that no traces of a methyl... 

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