Spirits

Rum.—This spirit may be divided into two main classes "Jamaica" and "Demerara." The greater proportion of the former is of the type usually imported into Britain. It is prepared by the fermentation of a wash consisting of cane molasses, scum drawn from the solution during the manufacture of cane sugar, "dunder" the viscous mass obtained from the bottom of the still during the previous operation, and "megass," the last, which is the fibrous part of the crushed cane, being added to promote fermentation. The fermentation is slow, extending to 12 days or even longer. When this operation is complete the spirit is distilled off in a pot still. There are two other types of Jamaica rum. That intended for local use is obtained by rapid fermentation and is of compara tively poor quality. The third, known as "German rum" has a very strong flavour and is used for blending purposes or for im parting to plain spirit the characteristics of ordinary rum. Demer ara rum is lighter in flavour than the Jamaica varieties and has a lower proportion of secondary ingredients. It is usually prepared by the fermentation of molasses dissolved in water, the spirit being then distilled off in patent stills or in pot stills of a type more complicated than those generally used in Jamaica. For the manu facture of industrial spirit, see ALCOHOL.

Spirits of Farinaceous Origin.—The raw materials used for these include cereal grains, such as barley, rye, oats, wheat, maize, etc., which produce whisky, "corn brandy," vodka, plain spirit and industrial alcohol. Potatoes are used in the manufacture of indus trial alcohol. The first stage in the preparation of spirit from starch is the conversion of the latter into dextrine-maltose and intermediate products. This is accomplished by the action of a diastatic ferment such as that present in malted grain (see BREW ING) or secreted by certain living organisms, or by ail acid such as sulphuric acid. The latter process is little employed at the present time. The materials employed by the distiller and the methods of preparation and treatment to which they are subjected before and after entering the distillery are in some respects similar to those employed by the brewer. The great difference, apart from the actual process of distilling, is that, whereas the object of the brewer is to produce beer, of which alcohol forms only a rela tively small proportion, the distiller, broadly speaking, desires to produce alcohol.

Malting.

Where malt is employed as the main raw material, as for instance in Scotch pot still and some other whiskies, the process of preparation usually does not differ widely from that used in making brewers' malt. The spirit manufacturer, however, need not be so particular as to the quality and character of the malt, which need only be sound and contain a high percentage of starch to serve his purpose. Barley intended for operations in a patent still is usually "steeped" and "floored" for periods longer than in brewery malting. In distilleries where barley malt is used not as a principal raw material but primarily as a diastatic agent, —for instance-in potato and maize distilleries—these two processes are particularly lengthy, the steeping being prolonged until the increase in weight due to the absorbed water is about 40 or 45%. The brewers' malt is almost invariably highly kilned in order to restrict the diastatic power. As the object of the distiller is to produce the highest proportion of alcohol possible he does not desire to restrict the diastatic power in this way, and if possible uses a green malt. The malt whisky manufacturer, however, de pends in great measure upon the kilning process to yield the char acteristic flavour of his product. For this reason, and also because of the difficulty of obtaining green malt in hot weather, a malt is often used which has undergone a mild kilning process in which a temperature of 130° F is seldom exceeded. In order to reduce

the danger of bacterial infection at subsequent stages some anti septic such as lime is introduced during the steeping.

Although green or low dried barley malt is the saccharifying agent usually employed both in the United Kingdom and on the Continent of Europe, malts prepared from other materials are not infrequently employed.

Oat malt, notwithstanding its low transforming power, possesses certain advantages, inasmuch as it is easily and rapidly prepared, it acts very quickly in the mash tun, and its diastatic power is well maintained during fermentation. Rye is best malted in con junction with a little barley or oats, as it otherwise tends to superheat and to grow together in a tangled mass.

Mashing and Fermentation.

The details of this stage of the process are, in the case of the malting, designed to produce the highest possible yield of alcohol consistent with the com mercial requirements, such as flavour and aroma, of the particular trade in which the distiller is engaged. In order to accomplish this the mashing takes place at a low temperature, the wort thus remaining unsterilized and the diastatic action continuing during the fermentation period. The problem for the distiller is to raise the mash to a temperature as high as possible in order to restrict the bacterial fermentation to which the wort is liable, whilst keep ing it sufficiently low to prevent the destruction of the diastase. The method employed varies according to the nature of the mash and the quality of the spirit desired, but in general principle is governed by the requirements indicated. The micro-organisms most to be feared are those belonging to the class of fission fungi (schizomycetes) such as the butyric, lactic, mannitic and mucic ferments. In order to avoid bacterial fermentation it is necessary either to let the wort "sour" naturally (lactic acid being chiefly formed) or to add a small quantity of acid (formerly sulphuric acid was frequently employed) to it before pitching the yeast. Such a condition is favourable to the free development of the desirable types of distillery yeasts but restrictive to the growth of brewery yeasts and especially of bacteria.

In order to facilitate the proper control of the formation of the acid the souring process is usually carried out in a small sepa rate mash so that when sufficient acid has been produced the tem perature of the liquid is increased and the acidifying process stopped. The souring mash is often inoculated with a special variety of lactic acid bacteria—a pure culture of B acidificans longissimus. The optimum developing temperature of this organ ism is about 104° F but it is better to keep the wort at F, for at that temperature practically no other bacteria is capable of development. When lactification is complete the temperature is raised to 165° F and after cooling the mass it is pitched with yeast and added to the main wort. Sometimes lactic acid is added instead of being produced naturally. Hydrofluoric acid and its salts are also sometimes used with very satisfactory results. Much of the yeast used in British and Irish pot still and in some patent still distilleries is obtained from breweries. In order to obtain a more rapid and complete fermentation a special type of "German yeast" is often used. It is usual to "pitch" at about 8o° F and then to cool slowly to 6o° F. As fermentation develops the temperature again rises naturally to about 85° F. In malt whisky distilleries the original gravity of the wort is usually about I.050 to 1.060, but in grain and potato distilleries it is often higher, being sometimes as high as I • I I in Germany. In the production of industrial alcohol other methods, involving the use of a pure culture of a micro organism in a sterilized wort and then a pure culture of yeast, are adopted. For details of these see