Dextrins roasting

A wide variety of special malts are produced which impart different flavor characteristics to beers. These malts are made from green (malt that has not been dried) or finished malts by roasting at elevated temperatures or by adjusting temperature profiles during kilning. A partial Hst of specialty malts includes standard malts, ie, standard brewers, lager, ale, Vienna, and wheat caramelized malts, ie, Munich, caramel, and dextrine and roasted products, ie, amber, chocolate, black, and roasted barley. 

Pyroconversion (dextrinization) Pyrodextrins - Prepared by dry roasting acidified starch... 

Preparation of Vanadium Oxychloride and Studying of Its Properties. Preparation of Vanadium Oxychloride by Roasting a Mixture of Vanadium(V) Oxide with Charcoal in a Chlorine Stream. Prepare a fine mixture of 5 g of vanadium(V) oxide, 3 g of charcoal, and 5 g of dextrin. Add water dropwise to the mixture until a paste... 

Preparation of Anhydrous Chromium(III) Chloride. Perform the experiment in a fume cupboard Grind 5 g of charcoal into a fine powder in a mortar, mix it with 12.5 g of chromium(III) oxide, add a thick starch size or a dextrin solution in cold water, and make beads about 5 mm in diameter from the mixture. Put the beads onto a clay dish and dry them in a drying cabinet at 110-120 °C. Next put them into an iron crucible, cover them with the charcoal powder and a lid, and roast them. 

Dextrins are produced by dry heating (roasting) starch in the presence of an acid catalyst. They are produced in a range of viscosity and color specifications. Dextrins are primarily used as adhesives in paper conversion, such as laminating and envelope production. A low-viscosity dextrin is used in Europe as a total chlorine free (TCF) coating binder for application on TCF paper. 

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. 

Fig. 13.—Solubility of Dextrins from Potato Starch, Depending on Roasting Time at 165° and pH 2.9. [Starch was acidified with (1) hydrochloric acid, (2) nitric acid, and (3) phosphoric acid.] ...

Almost all authors discussing the topic agree with one another that the viscosity of dextrins decreases quite suddenly in the first hour of dextrinization, to achieve an almost flat curve on further roasting. This is the case for British gums, as well as for acid-catalyzed dextrinization. A slight increase of viscosity is noted in the case of materials roasted for over 3 h at temperatures above 200°. This may be due to secondary polymerization of degradation products. On the other hand, the viscosity of yellow dextrins from com... 

XX and XXI) it revealed differences between the results for pyrodextrins obtained in the presence of an acid catalyst and for British gums. If the problem of roasting of starch in the presence of a catalyst is to be discussed in detail, dextrinization under the influence of acids, alk s, and oxidants must be considered separately. 

The authors of this Chapter have developed studies on dextrinization of potato starch in the presence of several or-amino adds. Conducted at 160-220°, this process yields light to dark brown solids bearing secondary aromas specific for roasted, baked, or fried foods. These aromas are dependent on the amino acid used, as well as on both the time and temperature of such reactions. Umano and Shibamoto showed the role of an amino acid (glycine) in the process of roasting of starch at 290°. 

Maturation is the next stage in the preparation of dextrins. It is necessary to allow the catalyst to penetrate into the starch granule, in order to correct imprecise distribution of acid, should this have happened in the first stage. The matured source is then subjected to drying, to avoid hydrolytic scission of the starch in the first period of roasting (as well as gelatinization, or... 

Conversion.—The conversion of starch results first in the so-called soluble starches, then in dextrin, then in maltose and finally in dextrose. The earlier stages of the process are not sharply defined from a chemical point of view and they are controlled entirely with a view to the special qualities desired in the product. As the conversion continues, mixtures of an unfer-mentable gum, dextrin, with varying proportions of maltose and dextrose are obtained. By carrying the process further, a yield of almost pure dextrose can be secured. This, of course, is the object in the processing of starch for the fermentation industry. The conversion of starch results either by the action of the enzyme, diastase, by boiling with dilute acids or by gentle roasting. The first two methods are used in the fermentation industry, often in conjunction with each other. 

Dextrins are the product of dry-roasting starch in the presence of an acid catalyst. Although potato, tapioca, and sago starches are the easiest to convert to dextrins, the low cost and ready availability of cornstarch, make it the most commonly used starch. Dextrins are generally divided into three categories white dextrins, canary or yellow... 

Dextrin—A water-based product derived from the acidification and/or roasting of starch. 

According to the Polish Standard PN-87/A-74820 modified starch is native starch processed in a mode that changes one or more of its initial physical or chemical properties [59], They include roasted starches (e.g., white and yeUow dextrins), acidic and alkaline starches (treated with respectively acids and bases), bleached starches, enzymatically modified starches, physically modified starches (usually heat-treated), and chanically modified starches (via incorporation of specified chemical compounds or via oxidation). These starches, except for the chanically modified ones, are acknowledged by legal regulations as native and are not treated as additives. Hence, the additive substances include the chemically modified starches. 

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