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BREWING CHEMISTRY

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Originally appearing in Volume V04, Page 513 of the 1911 Encyclopedia Britannica.
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BREWING See also:CHEMISTRY .—The principles of brewing technology belong for the most See also:part to physiological chemistry, whilst those of the cognate See also:industry, malting, are governed exclusively by that See also:branch of knowledge. Alike in following the growth of See also:barley in See also:field, its harvesting, maturing and See also:conversion into See also:malt, as well as the operations of mashing malt, fermenting wort, and conditioning See also:beer, physiological chemistry is needed. On the other See also:hand, the See also:consideration of the saline See also:matter in See also:waters, the See also:composition of the See also:extract of worts and beers, and the See also:analysis of brewing materials and products generally, belong to the domain of pure chemistry. Since the extractive matters contained in wort and beer consist for the most part of the transformation products of See also:starch, it is only natural that these should have received See also:special See also:attention at the hands of scientific men associated with the brewing industry. It was formerly believed that by the See also:action of diastase on starch the latter is first converted into a gummy substance termed dextrin, which is then subsequently transformed into a sugar—glucose. F. A. Musculus, however, in 1860, showed that See also:sugar and dextrin are simultaneously produced, and between the years 1872 and 1876 See also:Cornelius O'See also:Sullivan definitely proved that the sugar produced was maltose. When starch-See also:paste, the jelly formed by treating starch with boiling See also:water, is mixed with See also:iodine See also:solution, a deep See also:blue coloration results. The first product of starch degradation by either acids or diastase, namely soluble starch, also exhibits the same coloration when treated with iodine. As degradation proceeds, and the products become more and more soluble and diffusible, the blue reaction with iodine gives See also:place first to a See also:purple, then to a reddish See also:colour, and finally the coloration ceases altogether. In the same way, the See also:optical rotating See also:power decreases, and the cupric reducing power (towards See also:Fehling's solution) increases, as the See also:process of See also:hydrolysis proceeds.

C. O'Sullivan was the first to point out definitely the See also:

influence of the temperature of the mash on the See also:character of the products. The See also:work of See also:Horace T. See also:Brown (with J. See also:Heron) extended that of O'Sullivan, and (with G. H. See also:Morris) established the presence of an intermediate product between the higher dextrins and maltose. This product was termed maltodextrin, and Brown and Morris were led to believe that a large number of these sub-stances existed in malt wort. They proposed for these substances the generic name "amyloins." Although according to their view they were compounds of maltose and dextrin, they had the properties of mixtures of these two substances. On the See also:assumption of the existence of these compounds, Brown and his colleagues formulated what is known as the maltodextrin or amyloin See also:hypothesis of starch degradation. C. J.

Lintner, in 1891, claimed to have separated a sugar, isomeric with maltose, which is termed isomaltose, from the products of starch hydrolysis. A. R. See also:

Ling and J. L. See also:Baker, as well as Brown and Morris, in 1895, proved that this isomaltose was not a homogeneous substance, and See also:evidence tending to the same conclusion was subsequently brought forward by See also:continental workers. Ling and Baker, in 1897, isolated the following compounds from the products of starch hydrolysis —maltodextrin-a, C36H62O31, and maltodextrin-(3, Cz1H.12O21(previously named by See also:Prior, achroodextrin III.). They also separated a substance, C12H22O11, isomeric with maltose, which had, however, the characteristics of a dextrin. This is probably identical with the so-called dextrinose isolated by V. Syniewski in 1902, which yields a phenylosazone melting at 82-83° C. It has been proved by H. Ost that the so-called isomaltose of Lintner is a mixture of maltose and another substance, maltodextrin, isomeric with Ling and Baker's maltodextrin-j3.

The theory of Brown and Morris of rthe degradation of starch, although based on experimental evidence of some See also:

weight, is by no means universally accepted. Nevertheless it is of considerable See also:interest, as it offers a rational and consistent explanation of the phenomena known to accompany the transformation of starch by diastase, and even if not strictly correct it has, at any See also:rate, proved itself to be a See also:practical working hypothesis, by which the mashing and fermenting operations may be regulated and controlled. According to Brown and Morris, the starch See also:molecule consists of five amylin See also:groups, each of which corresponds to the molecular See also:formula (Cr2H2oO1)20. Four of these amylin radicles are grouped centrally See also:round the fifth, thus: (C12H20010)20 (C12H20O10)20 < (C12H20O1 )20 C12H201o)20 By the action of diastase, this complex molecule is split up, undergoing hydrolysis into four groups of amyloins, the fifth or central See also:group remaining unchanged (and under brewing conditions unchangeable), forming the substance known as See also:stable dextrin. When diastase acts on starch-paste, hydrolysis proceeds as far as the reaction represented by the following See also:equation: 5(C12H20O1o)20+8o See also:H2O=8o C12H22O11+ (Cl2H2o01o)20 starch. water. maltose. stable dextrin. The amyloins are substances containing varying See also:numbers of amylin (See also:original starch or dextrin) groups in See also:conjunction with a proportional number of maltose groups. They are not separable into maltose and dextrin by any of the See also:ordinary means, but exhibit the properties of mixtures of these substances. As the process of hydrolysis proceeds, the amyloins become gradually poorer in amylinand relatively richer in maltose-groups. The final products of f transformation, according to Brown and J. H. See also:Millar, are maltose{ and See also:glucose, which latter is derived from the hydrolysis of the stable dextrin. This theory may be applied in practical brewing in the following manner.

Phoenix-squares

If it is desired to obtain a beer of a stable character—that is to say, one containing a considerable proportion of high-type amyloins—it is necessary to restrict the action of the diastase in the mash-See also:

tun accordingly. On the other hand, for mild See also:running See also:ales, which are to " See also:condition " rapidly, it is necessary to provide for the presence of sufficient maltodextrin of a See also:low type. Investigation has shown that the type of maltodextrin can be regulated, not only in the mash-tun but also on the malt-See also:kiln. A higher type is obtained by low kiln and high mashing temperatures than by high kiln and low mashing heats, and it is possible therefore to regulate, on scientific lines, not only the quality but also the type of amyloins which are suitable for a particular beer. The chemistry of the nitrogenous constituents of malt is equally important with that of starch and its transformations. Without nitrogenous compounds of the proper type, vigorous fermentations are not possible. It may be remembered that yeast assimilates nitrogenous compounds in some of their simpler forms—amides and the like. One of the aims of the maltster is, therefore, to break down the protein substances See also:present in barley to such a degree that the wort has a maximum nutritive value for the yeast. Further, it is necessary for the See also:production of stable beer to eliminate a large proportion of nitrogenous matter, and this is only done by the yeast when the proteins are degraded. There is also some evidence that the presence of albumoses assists in producing the foaming properties of beer. It has now been established definitely, by the work of A. Fernbach, W.

Windisch, F. See also:

Weiss and P. Schidrowitz, that finished See also:medal of the society; and in 1816 the See also:French See also:Institute awarded malt contains at least two proteolytic enzymes (a peptic and a pancreatic See also:enzyme). The presence of different types of See also:phosphates in malt, and the important influence which, according to their nature, they exercise in the brewing process by way of the enzymes affected by them, have been made the subject of See also:research mainly by Fernbach and A. See also:Hubert, and by P. E. See also:Petit and G. Labourasse. The number of enzymes which are now known to take part in the brewing process is very large. They may with utility be grouped as follows: Name. Role or Nature. Cytase .

. . . Dissolves See also:

cell walls of starch granules. Diastase A Liquefies starch. In the malt . . . Saccharifies starch. Diastase B . . . or mash-tun. Proteolytic Enzymes () Peptic. (22) Pancreatic. Catalase .

. . . Splits peroxides. Inverts See also:

cane sugar. . Splits maltose into glucose. Splits sugar into See also:alcohol and carbonic See also:acid.

End of Article: BREWING CHEMISTRY

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