Page:1902 Encyclopædia Britannica - Volume 26 - AUS-CHI.pdf/404

 362

BREWING

The repeal of the Malt Acts has been responsible for at least one considerable modification in the process of malting, namely, the abandoning of the couch. It is true that some maltsters still make use of it, but there can be little doubt that the piling up of the freshly-steeped grain in heaps for any length of time is not only unnecessary but undesirable, as it leads to unevenness of growth on the floors. The conditions necessary for the treatment and modification of unkindly barleys, both as regards the starch and the nitrogenous matters, have formed the subject of many investigations, the results of which have largely added to the maltster’s resources. These investigations can only be indicated here, but it may be sufficient to say that our knowledge of the influence of temperature (on the floors as well as on the kiln) of the merits of prolonged slow flooring as opposed to a more rapid (so-called “ forced ”) growth, and of other kindred considerations, has been very considerably increased. It has been shown that the “ forcing ” process, which consists essentially in the employment of relatively high floor temperatures in order to accelerate rootlet growth, is liable to lead to unsatisfactory clarification—at any rate, when brewing on infusion lines—and that better results are obtained by prolonged flooring at lower temperatures. It also appears fairly certain that the total quantity of nitrogen in a barley or a malt is no criterion of its value, but that it is the condition of the nitrogenous matter which is of importance, and more particularly the proportion of coagulable to non-coagulable albuminoids (Morris, Kukla, &c.). The methods for controlling the value of a barley or malt in the laboratory have also been much elaborated, and it is now possible, within certain limits, to determine by a laboratory examination whether a barley or a malt is satisfactory or not, what the methods of treatment should be in the malt-house or the brewery, and so on. If the technical operations have made considerable advances it is to a great extent due to the fact that the objects to be attained and the processes taking place during malting are now much better understood. The results of some of the more important modern investigations —in this connexion the work of Messrs O’Sullivan, and Brown and Morris must be specially mentioned—may be briefly summed up as follows. During the periods of steeping and germination there is in the first place formed a substance called cytase, the principal function of which is to break up or liquefy the envelope of cellulose with which each grain of the starch proper—the granulose—in the barley corn is surrounded, and so to prepare the way for the action of the diastase. The latter is unable to act until this transformation of the cellulose sheath has taken place. Cytase is one of a class of bodies which were formerly called “ferments,” but are now termed “enzymes” in order to distinguish them from living micro-organisms such as the yeasts and bacteria. The “ enzymes ” are unorganized (i.e., without biological structure or life) products formed in the course of the metabolic processes exhibited by the living cell, and they possess a certain specific action or actions which they are able to exercise outside or independently of the organism by which they are produced. It is characteristic of these substances—and in this they are sharply differentiated from the ordinary chemical reagents—that the amount of work they can do (transforming, liquefying, saccharifying, &c.) stands in no definite relation to the quantity of the enzyme. Messrs Brown and Morris have shown that immediately the germinating process in the barley corn begins, the embryo commences to secrete diastase, which diffuses into the endosperm and there quickly starts its attack on the cellulose (modified by the previous action of the cytase) and the starch immediately below the scutellum. This formation of diastase takes place principally, if not indeed entirely, in the epithelium, and is favoured by the presence of small quantities of acid, but restricted almost completely by readily assimilable carbohydrates (sugars). Thus, if barley be germinated in such a way that a sufficient quantity of cane sugar for the nourishment of the embryo is always present, no diastase is formed, and it is therefore probable that the diastatic secretion of the epithelium is an example of the starvation processes well known to botanists. The action of diastase is twofold, liquefying and saccharifying; that is to say, it both makes the starch soluble in water and also

converts it into sugar. It is probable that there are at least three distinct enzymes contained in malt diastase ; one liquefies starch, a second saccharifies the same, and a third (a peptonizing enzyme) is responsible for the modification of the nitrogenous matters. There is a certain quantity of saccharifying diastase in ungerminated barley, but it possesses no liquefying action. During the process of germination the proportion of this saccharifying diastase is enormously increased, and at the same time the liquefying enzyme is formed and stored for future use. Green malt ordinarily contains a large excess of diastase, especially of the saccharifying variety, and this in itself—apart from other reasons—makes its direct employment in the mash-tub impracticable, but it is necessary that it should contain a very large excess, as the kilning process destroys the diastatic activity of the green malt to a greater or lesser extent. It is now known that the partial conversion of the insoluble albuminous substances into the soluble forms is one of the most important results of the malting process. An excess of insoluble albuminoids not only causes difficulties in clarification, but tends to promote the growth of undesirable micro-organisms in the finished beer. Hilger and van der Becker give the following figures as an example of the increase of the soluble albuminoids during malting:— Percentage of Total Nitrogen. 6'74 per cent, of soluble nitrogen. Barley 375 Steeped barley. 21-96 Green malt 24-44 ,, „ Cured ,, There is considerable divergence of opinion as to the nature of the soluble bodies formed, but they certainly appear to include coagulable proteids, albumoses, amides, amido-acids, and substances which, if they are not peptones proper, are at any rate very similar to the latter. Considerable changes also take place during germination in regard to the disappearance of starch and the formation of sugar. The disappearance of starch varies from 4 to 20 per cent. Part of this is lost altogether in the shape of carbonic acid and water, a part is used for the formation of tissue, and the remainder is transformed into cane and other sugars (Brown and Morris, T. C. Day, Kjeldahl, O’Sullivan, &c.). At the same time there is a decrease in the percentage of fat and inorganic salts, but a considerable increase of acid —principally lactic acid. Malt Substitutes. — Prior to the repeal of the Malt Acts the only substitute for malt allowed in the United Kingdom was sugar (Fig. 4). The quantity of the latter employed Fig. 4.—Diagram showing graphically the total was 295,865 cwt. in quantities (bushels) of (a) malt and corn and malt substitutes used in brewing in the 1870, 868,943 cwt. in (6) United Kingdom in the years 1875, 1885, 1891, 1899. 1875, and 1,136,434 bushel.)(Malt substitutes at 28 ib to the cwt. in 1880—the last year prior to the passing of the new Act. Since then the figures have shown a steady advance, reaching 2,025,658 cwt. in 1890, and 2,980,039 cwt. in 1900; that is to say, they have practically trebled within twenty years. At the same time other substitutes, such as unmalted corn and preparations of rice and maize, have come into favour, the quantity of these substances used being in 1899, 218,889 bushels of unmalted corn, and 1,087,538 cwt. of rice, maize, &c. These figures appear all the more striking when it is stated that the quantity of malt converted into beer has not increased since 1878. The following statistics with regard to the use of malt substitutes in the United Kingdom are not without interest:—