Page:1902 Encyclopædia Britannica - Volume 26 - AUS-CHI.pdf/407

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BREWING are quite harmless per se, but impart an unpleasantly rough and bitter taste to the beer. Mashing. — The writer has already alluded to and attempted to give reasons for the fact that in recent times the trend of brewing has been in the direction of light, bright beers, and there is no doubt that in many respects the modern product is preferable to the highly alcoholic, heavily-hopped beers of the bygone generation. When this class of beer is well and cleanly brewed from good material and the fermentation has proceeded on satisfactory lines, it is not only more palatable and sightly, but also less intoxicating and more easily digestible than the beer consumed by our predecessors. Although the imports of foreign beer into the United Kingdom are still infinitesimal compared with the total quantity consumed, it seems that the British taste for beer brewed on the German principle or some modification thereof is steadily growing. Within the most recent times the laying down of a lager beer plant by Messrs Allsopp, capable of turning out 50,000 barrels yearly—i.e., a liquid quantity practically equal to the total imports of foreign beer—has created a very widespread interest. The ordinary German beer—commonly called “ Lager ” in Great Britain (the German name for it is Export Bier, the term Lager being reserved for a somewhat different class of brew)—is produced on totally different lines from English beer. The latter is brewed by a process of infusion, the former according to the decoction system, so called because portions of the mash are treated separately from the whole. The method pursued in the decoction system is as follows:—-After the grist has been mashed with cold water until a homogeneous mixture ensues, sufficient hot water is introduced into the mash-tun to raise the temperature to 85°-100° F. according to circumstances. Thereupon roughly one-third of the mash (including the “goods”) is transferred to the maisch Kessel (mash copper) in which it is gradually brought to a temperature of (about) 166° F., and this heat is maintained until the mash, which at first presents a milky appearance, becomes transparent—a sign that the starch is completely converted. The Dickmaische, as this portion is called, is then raised to the boiling-point and the ebullition sustained between a quarter and three-quarters of an hour. Just sufficient of the Dickmaische is returned to the mash-tun proper to raise the temperature of the whole to 110o-125° F., and after a few minutes a third is again withdrawn and treated as before, to form the second Dickmaische. When the latter has been returned to the mash-tun the whole is thoroughly worked up, allowed to stand in order that the solids may deposit, and then another third, which is now, however, practically a clear wort (called the Lautermaische), is withdrawn, boiled by itself until the coagulable albuminoids are thoroughly precipitated, and finally reconveyed to the mash-tun, where the mashing is continued for some time, the final heat being rather over 160° F. (See under “Fermentation.”) As to the relative character and stability of decoction and infusion beers, the latter are, as a rule, more alcoholic; but the former contain more unfermented malt extract, and are therefore, broadly speaking, more nutritive. Beers of the German type are also less heavily hopped and more peptonized than English beers, and more highly charged with carbonic acid, which, owing to the low fermentation and storing temperatures, is retained for a comparatively long time, and keeps the beer in condition. On the other hand infusion beers are of a more stable and stimulating character. It is impossible to keep “ lager ” beer on draught in the ordinary sense of the term m England. It will not keep unless placed on ice, and, as a matter of fact, the “ condition ” of lager is dependent to a far greater extent on the methods of dis-


tribution and storing than is the case with infusion beers. If a cask is opened it must be rapidly consumed; indeed, it becomes undrinkable within a very few hours. The gas escapes rapidly when the pressure is released, the temperature rises, and the beer becomes flat and mawkish. In Germany every publican is bound to have an efficient supply of ice, the latter frequently delivered by the brewery together with the beer. The following comparative analysis may give the reader some idea of the difference in composition of various Continental and English beers :— Beer. ( Stout English J Pale Ale . Beers | Light Bitter ^Mild Ale . German ( Munich Lager &c. -J Munich Export Beers ( Pilsener .

Total Solids Alcohol (Extract) per Cent. per Cent. 5-27 435674-

6-11 5-58 3-34 4'54 343-39

Original Gravity of Wort. 1-0648 1-0579 1-0394 1-0554 1-0523 1-0595 1-0416

It was formerly believed that by the mashing process the starch of the malt is first converted into dextrin, and that a part of the latter is then transformed into glucose ; but modern investigations have shown that the diastatic degradation of starch is by no means so simple a matter. In the first place we now know that the final product obtained from starch under brewing conditions is not glucose, but maltose. It is held by some authorities that the latter is split up into glucose prior to fermentation; but this is certainly not the case in the mash - tun. Although not yet universally accepted, the theory of starch degradation propounded by Messrs Brown and Morris, usually known as the amylo'in or malto-dextrin theory, and which is based on a great mass of experimental evidence, is of considerable interest, and not only offers a rational and consistent explanation of the phenomena known to accompany the transformation of starch by diastase, but has proved itself to be a practical working hypothesis by which the mashing and fermenting operations may be regulated and controlled. According to Messrs Brown and Morris, the starch molecule consists of five amylin groups, each of which corresponds to the molecular formula (C12H2o010)2o. Four of these amylin radicles are grouped centrally round the fifth thus :— [CjoELoOioL /[Ci2H2o010]20


[Cj2H2oOio]o0 tCi2H2o010]2o By the action of diastase this complex molecule is split up, undergoing hydrolysis into four groups of amyloins, the fifth or central amylin group remaining unchanged (and under brewing conditions unchangeable), forming the substance known as stable, dextrin. The following equation explains the primary transformation :— Starch. Water. Stable Dextrin. Amyloins of various types. The amyloins are substances containing varying numbers of amylin (original starch or dextrin) groups in conjunction with a proportional number of maltose radicles. They are not separable into maltose and dextrin by any of the ordinary means, but exhibit the properties of both these substances. As the process of hydrolysis and degradation proceeds the amyloins become gradually poorer in amylin and relatively richer in maltose groups, the final product of transformation being maltose. The progress of the transformation of the four convertible amylin groups into malto-dextrins, first of a high and then of a lower type, and finally into maltose, is accompanied by characteristic changes in the physical and chemical properties of the products of hydrolysis. The “opticity”—that is, the power of rotating a ray of polarized light—gradually diminishes, and, inversely, the cupric reduction, by which is denoted the capacity for reducing an alkaline solution of tartrate of copper (Fehling’s solution), increases. Messrs Brown and Morris have shown that there is a direct relationship between the opticity and the cupric reduction exercised by the mixed products of starch conversion, and also of any fraction of those mixed products. This relationship is so exact that if either the opticity or the cupric reduction of a solution of starch conversion products of a known density is observed, the other factor can be obtained by calculation. In the