Dextrin

“ Commercial dextrin, which is much used in the preparation of mucilages and adhesive pastes, is prepared by heating dry starch to about 250° C. It is composed chiefly of achroo-dextrin, mixed with varying quantities of erythro-dextrin and glucose.
Glycogen, or "animal starch," is one of the most widely distributed reserve foods of the animal body; in fact, it is the only known form of carbohydrate-reserve in animal tissues. But it is present only rarely in plants. It occurs in certain fungi, particularly in yeasts. In the animal body, glycogen is found in all growing cells ”

“ For instance much of the gum used in the arts is made by heating starch. The outside of the loaf in the oven gets hot enough for some of the starch to be converted into dextrin. Dextrin is soluble in water like sugar and so appears with sugar in the analyses of bread. From the point of view of food-value this is of no consequence, as dextrin and sugar serve the same purpose in nutrition, and have almost the same value as each other and as starch. 113
Bread always contains a little fat, not as a rule more that one or two per cent. ”

“ The substance which in a measure produces this quality is called mucilage by Maumené and some others. Others, again, have given it different names. Maumené says that it seems to be a sort of intermediary substance between cellulose and dextrin, and [Pg 192] that its nature is not yet known, but that it is a near neighbor of sugar. ”

“ The starch which we take so abundantly as food appears to have no more food-value to us than to the vegetable germ until the conversion into dextrin or sugar is effected. From what I have already stated concerning the action of heat upon starch, it is evident that this conversion is more or less effected in some processes of cookery. In the baking of bread an incipient conversion probably occurs throughout the loaf, while in the crust it is carried so far as to completely change most of the starch into dextrin, and some into sugar. ”

“ If a mixture of filtered potato starch paste and erythrodextrin is dried in a watch glass covered with a thin pellicle of collodion, and a drop of iodine solution placed on the latter, it penetrates very slowly through the pellicle, the dextrin becoming first tinctured with red, and the granulose afterward with blue. If, on the other hand, no erythrodextrin is used, the diffusion of the iodine causes at once simply a blue coloring. ”

“ Huber and Snow improved the method greatly by floating the paraffin sections directly on to warm dilute sugar-dextrin (a 10 per cent solution of Schmorl’s stock-solution will suffice) , and plating the sections directly from the latter. This method of using the dilute solution is less expensive, much cleaner, and saves time in drying in the incubator. The results are in every way better than with the Schmorl solution in full strength. The formation of bubbles and crystals is almost wholly prevented, and less dust is caught on the plate. ”

“ With inferior flour dextrin is formed inside the loaf to some extent as well as on the outside, consequently bread made from inferior flour rises badly and is darker in colour. This inferior flour is made sometimes from wheat that has been damp, the dampness causing the soluble albumenoids which the grain contains to act on the insoluble gluten, decomposing it into soluble bodies, and producing dextrin by their action on the starch in the grain. ”

“ The amyloins are substances containing varying numbers of amylin (original starch or dextrin) groups in conjunction with a proportional number of maltose groups. They are not separable into maltose and dextrin by any of the ordinary means, but exhibit the properties of mixtures of these substances. As the process of hydrolysis proceeds, the amyloins become gradually poorer in amylin and relatively richer in maltose-groups. The final products of transformation, according to Brown and J. H. Millar, are maltose and glucose, which latter is derived from the hydrolysis of the stable dextrin. ”

“ If instead of at once saturating the diluted acid with chalk, we boil it for four or five hours, the dextrin is entirely converted into grape sugar (glucose) , which, by the addition of chalk and filtration, as before, and evaporation at a gentle heat to the consistence of a syrup, will, after repose for a few days, furnish a concrete mass of crystallised sugar. Cotton, linen, or unsized paper, thus treated, yield fully their own weight of gum and one-sixth of their weight of grape sugar. ”

“ In a grain of wheat, for example, the embryo is surrounded with its first food. While the seed remains dry above-ground there is no assimilation of the insoluble starch or gluten, no growth, nor other sign of life. But when the seed is moistened and warmed, the starch is changed to dextrin by the action of diastase, and the dextrin is further converted into sugar. The food of the germ thus gradually rendered soluble penetrates its tissues ”

“ As it is rather expensive, it is seldom used by itself as a cement.
Dextrine is extensively used in place of gum arabic in printing wall-papers, for stiffening and glazing cards and paper, for thickening the colors of calico printers, in making mucilages, etc. It is prepared by heating starch previously moistened with nitric acid in an oven, and can also be produced by heating paste with malt extract or very dilute sulphuric acid. ”

“ The dexter chief point is a point in the right-hand upper corner of the shield, being in the dexter extremity of the chief.
Dex ́trine, or British Gum, (C6H10O5) x, a generic name applied to soluble gummy substances intermediate between starch and glucose. They are prepared from starch by the aid of dilute mineral acids or of enzymes, and are usually named according to the colour they give with iodine, e.g. erythro-dextrine, &c. When heated with dilute acids, they are transformed into glucose. They are white, odourless substances, and are good substitutes for gum-arabic. ”

“ There are other means of changing starch into dextrine than by heat, one of the most remarkable of which is diastase, a substance found in sprouting grains, which has the power to transform the starch stored in the grain by nature into soluble dextrine, in which form it can be taken up by the young plant for food. The crude starch could not thus be absorbed. The starch which we use as food is of no more value to us than it is to the young plant until it has been changed into dextrine or sugar. ”

“ Dextrine, deks′trin, n. starch altered by the action of acids, diastase, or heat till it loses its gelatinous character, so called because when viewed through polarised light it turns the plane of polarisation to the right.—n. Dex′trose, a glucose sugar, found in grapes, &c., and manufactured from starch by means of sulphuric acid. ”

“ When completely hydrolyzed, the polysaccharides yield only hexoses. They are, therefore, technically known as "hexosans." Each individual polysaccharide which has been studied thus far yields only a single hexose, although the particular hexose obtained varies in different cases. In fact, the polysaccharides are often classified according to the hexoses which they yield on hydrolysis, into the following groups: the dextrosans, which yield glucose, and include starch, dextrin, glycogen, lichenin, etc.; the levulosans, which yield fructose, and include inulin, graminin, triticin, etc. ”

“ I find that oatmeal-porridge, when thus treated with malt or malt extract, is thinned by the conversion of the bulk of its insoluble starch into soluble dextrine; that boiled rice is similarly thinned; that a stiff jelly of arrowroot is at once rendered watery, and its conversion into dextrine is demonstrated by its altered action on a solution of iodine. Instead of instantly striking a blue-black color on admixture, only a slight brownish tinge is displayed, and not even this when the temperature has been carefully maintained. ”

“ The product is the commercial glucose or corn syrup, which may if desired be evaporated to a white powder. It is a mixture of three derivatives of starch in about this proportion:
There are also present three- or four-tenths of one per cent. salt and as much of the corn protein and a variable amount of water. It will be noticed that the glucose (dextrose) , which gives name to the whole, is the least of the three ingredients.
Maltose, or malt sugar, has the same composition as cane sugar (C12H22O11) , but is not nearly so sweet. Dextrin, or starch paste, is not sweet at all. ”

“ Postage stamp mucilage can be made by dissolving an ounce of dextrine in five ounces of hot water, and adding one ounce of acetic acid and one ounce of alcohol. The dextrine should be dissolved in water in a glue pot, or some similar vessel, which will prevent burning. The quantities in this recipe may be varied by taking any required weights in the proportions mentioned. Dr. Phin says that dextrine mixed with water makes a good label mucilage if a drop or two of glycerine be added to it. Too much glycerine will prevent the mucilage drying; with too little it will be likely to crack. ”

“ British gum or dextrine is prepared by heating starch. It varies considerably in composition—sometimes being only slightly roasted and consequently only partly converted into dextrine, and at other times being highly torrefied, and almost completely soluble in cold water and very dark in colour. Its thickening power decreases and its “ gummy ” nature increases as the temperature at which it is roasted is raised. ”

“ Compounds of vegetable origin are widely advertised, but they often contain dextrine and gum, both of which are dangerous, as they coat the tubes with a compact scale, not permitting the water to reach the iron. ”

“ The comparatively fixed class, as regards diffusion, is represented by a different order of chemical substances (marked out by the absence of the power to crystallise) , which are slow in the extreme. Among the latter are hydrated silicic acid, hydrated alumina, and other metallic peroxides of the aluminous class, when they exist in the soluble form; with starch, dextrine, and the gums, caramel, tannin, albumen, gelatin, vegetable and animal extractive matters. Low diffusibility is not the only property which the bodies last enumerated possess in common. ”

“ COPYING PAD.—White Gelatine four ounces, Water eight ounces, Glycerine eight ounces, Gum Dextrine two ounces. Always use these same proportions for any amount. Melt the Gelatine in the water at a gentle heat, add to it the Glycerine, in which the Gum Dextrine has been thoroughly incorporated. Now stir all together until thoroughly mixed and then pour into pans of the desired size, to the depth of one-half inch.
Recipe for Ink to Be Used.—Violet Analine forty grains, Gum Arabic twelve grains, Alcohol one-fourth ounce, Water one-half ounce. ”

“ It dissolves in water and dilute alcohol; by strong alcohol it is precipitated from its solutions as the hydrated compound, C6H10O5⋅H2O. Diastase converts it eventually into maltose, C12H22O11; and by boiling with dilute acids (sulphuric, hydrochloric, acetic) it is transformed into dextrose, or ordinary glucose, C6H12O6. It does not ferment in contact with yeast, and does not reduce Fehling's solution. If heated with strong nitric acid it gives oxalic, and not mucic acid. ”

“ The ester solution was then put in a vacuum desiccator over sulphuric acid and the alcohol evaporated. A black, tarry, solid mass was left having the ester odor. It was extracted with warm water and filtered from insoluble tar. The filtrate had a green color and the ethereal odor. It was shaken out with ether; the ether layer had a blood-red color while the water layer was deep green. [Pg 16] The extraction with ether was continued until the water layer was no longer green. The combined ether extracts were evaporated in a desiccator without heat. ”

“ The barium and iron acids although different chemically, have some groups in common as shown by the formation of a common oxidation product. There are at least three alcohol radicals formed through hydrolysis, a resinous alcohol radical, a crystalline substance with a melting point of 130 degrees, and a volatile oil.
[Pg 44]
The physiological action of the Ava is due to the ester resins. The two resinous acids formed through the hydrolysis of these esters seem to be the two active constituents of the resin ester. ”

“ In the oxydative disintegration of dextrose, taking place in aërobic organisms, if sufficient quantities of oxygen are present, there occurs a splitting up of the carbohydrate molecule, as a result of the introduction of oxygen, into simpler substances and finally into carbon dioxide and water, just as the dextrose molecule, when subjected to oxydative processes, is split up into simpler molecules. In the living substance the oxydases play the important rôle of oxygen carriers. ”

“ Mix the solution well, pour through a dry filter and determine the dextrose in an aliquot. Conduct a blank determination upon the same volume of the malt extract as used upon the sample, and correct the weight of reduced copper accordingly. The weight of the dextrose obtained multiplied by 0.90 gives the weight of starch. ”

“ Water, which gives an acid or alkaline reaction, leads inevitably to erroneous results. Ninhydrin reacts not only with albumen and albuminous decomposites, but under certain conditions with other compounds as well, for instance, sugar. [3] No trouble can be caused by these, if distilled water be used. The organ cannot give off any non-albuminous substances, which will affect the reaction of the fluid, if it is boiled in the manner prescribed. There could not possibly be any carbohydrates left, and we have the control test with serum to fall back on, in any case. ”