LIQUORS.
The ordinary forms of liquors (namely, whisky, rum, and gin), are prepared by the distillation of alcoholic infusions. The process of distillation is preceded either by the conversion of the amylaceous constituents of grain, first into sugar, then into alcohol, or by the fermentation of saccharine bodies into alcohol, or, as in the case of brandy, it may be directly applied to a solution containing alcohol.
Brandy.—When genuine, brandy is the product of the distillation of various sorts of rich, light-coloured wines. The most esteemed quality is prepared in the neighbourhood of Cognac, in the Deux Charentes district, and in Armagnac; but numerous inferior grades are manufactured in Rochelle and Bordeaux and in other parts of Southern France, as well as in Spain and Portugal. In the United States, a considerable quantity is produced by the distillation of California and Ohio wine. The fermented marc and lees of grapes are also extensively utilised in the manufacture of brandy. Most of the liquor known in commerce under this name, however, is made from the spirit obtained by the distillation of potatoes, corn, and other grains, which is subsequently rectified, deodorised, and then suitably flavoured. In France, the different grades of brandy are known as eau-de-vie supérieure (the best quality of Cognac); eau-de-vie ordinaire (common, sp. gr. 0·9476); eau-de-vie de marc (chiefly used for mixing purposes); eau-de-vie seconde (weak and inferior); eau-de-vie à preuve de Hollande (sp. gr. 0·941); eau-de-vie à preuve d’huile (sp. gr. 0·9185); eau-de-vie forte (sp. gr. 0·8390); and esprit-de-vin (sp. gr. 0·8610).
The characteristic taste and bouquet of the original wine are to a considerable extent communicated to the resulting brandy, and upon these qualities its value is greatly dependent. Many of the remarks made in regard to the ageing, flavouring and blending of wines equally apply to brandy, and need not be repeated in this place. When freshly distilled, it is colourless, its amber tint being either due to the casks in which it has been stored, or to added caramel. The normal constituents of genuine brandy are water, alcohol (including small amounts of butylic, propylic and amylic), various ethers (acetic, oenanthic, butyric, and valerianic), aldehyde, acetic and tannic acids, and traces of sugar and the oil of wine. The specific gravity usually approximates 0·9300 (equivalent to 52 per cent. of alcohol by volume), it may, however, range from 0·9134 to 0·9381 (from 60 to 48 per cent. of alcohol). Owing to the presence of acetic acid, genuine brandy usually shows a slightly acid reaction. According to Blyth, the constituents vary as follows:—total solids, from 1 to 1·5 per cent.; ash, from ·04 to ·2 per cent.; acids (estimated as tartaric), from ·01 to ·05 per cent.; sugar from 0 to ·4 per cent. A partial examination of brandy, by König,[111] furnished the following percentages:—specific gravity, 0·8987; alcohol (by weight), 61·70; extract, 0·645; ash, 0·009. The ingredients found in twenty-five samples of brandy tested for the New York State Board of Health varied as follows:—specific gravity, 0·9297 to 0·9615; alcohol (by weight) from 25·39 to 42·96; extract, from 0·025 to 1·795; ash, from 0·002 to 0·014.
The majority of these samples were certainly abnormal in composition. Ordonneau[112] has quite recently determined by careful fractional distillation the proportions of the more important constituents of cognac brandy twenty-five years old, with the following results, the quantities being stated in grammes per hectolitre:—aldehyde, 3; ethylic acetate, 35; acetal, traces; normal propylic alcohol, 40; normal butylic alcohol, 218·6; amylic alcohol, 83·8; hexylic alcohol, 0·6; heptylic alcohol, 1·5; propionic, butyric and caproic ethers, 3; oenanthic ether, 4; amines, traces. The large proportions of normal butylic and amylic alcohols obtained are very significant. It was found that commercial alcohol, prepared from corn, potatoes and beetroot, while containing isobutylic alcohol, was entirely free from normal butylic alcohol, and the difference in flavour between genuine brandy and brandy distilled from grains would appear to be mainly due to this fact. Normal butylic alcohol is obtained when fermentation takes place under the influence of elliptical or wine yeast, whereas the iso-alcohol is the product of fermentation induced by means of beer yeast; and it was shown that, by fermenting molasses, etc., with the aid of wine yeast, a spirit was obtained which much resembled brandy in colour and flavour.
Whisky.—Whisky is the spirituous liquor prepared by distilling fermented infusions of barley, wheat, corn, and other grains. Spirits that contain over 60 per cent. of alcohol are known as “high wines,” or common spirits; those containing 90 per cent. of alcohol are often termed “cologne spirits,” the name whisky being usually given to the product of a former distillation, containing about 50 per cent. by weight of alcohol. In Great Britain, the largest amount of whisky is made in Scotland and Ireland; in the United States, the principal supply comes from the States of Illinois, Ohio, Indiana, Kentucky (Bourbon Co.), and Pennsylvania (Monongahela Co.). The grains taken differ greatly in composition. In Scotland and Ireland, malted barley (pure, or mixed with other grain) is extensively employed; in the preparation of Bourbon, partially malted corn and rye are taken, while, for Monongahela whisky, only rye (with 10 per cent. of malt) is used. The essential features of whisky-making are, first, the conversion of the starch of the grain into dextrine and glucose, which takes place in the process of mashing; the change being due to the action of the nitrogenous principle, diastase (formed during the germination of the gain); then, the transformation of the sugar into alcohol and carbonic acid by fermentation, which is induced by the addition of yeast; and, finally, the concentration of the alcohol by distillation. The quality of whisky is much affected by the nature of the grain from which it is prepared, and by the care exercised in its manufacture, more particularly in the process of distillation. The most injurious ingredient in distilled spirits is commonly known as “fusel oil,” which term comprises several products of alcoholic fermentation, possessing a higher boiling point than ethylic alcohol, and consisting chiefly of amylic alcohol, accompanied by small proportions of butylic and propylic alcohols. Several varieties of fusel oil exhibiting distinctive properties are met with, but that obtained from potato-spirit is the most common. As a rule, the spirits prepared from malted grain contain the smallest proportion. In the manufacture of whisky, a danger of promoting the formation of fusel oil is incurred by carrying on the distillation to the furthest point, in order to obtain the greatest possible quantity of alcohol. In Great Britain, the fermented mash is removed from the remaining grain before its introduction into the still; but in this country the entire mash is occasionally taken, by which means a larger yield of alcohol is supposed to be effected. This practice is evidently open to the objection that the solid matters of the wort are liable to suffer destructive distillation, and engenders the formation of fusel oil. Another result, sometimes experienced, is the imparting of a smoky flavour to the product, which was originally intentionally communicated to the famous “poteen” whisky of Ireland, by using malt dried by means of burning turf. This quality is said to be still artificially obtained by the use of creosote. Genuine whisky, when recently made, is nearly colourless; but, if preserved in casks, it gradually acquires a brownish colour. It contains minute quantities of tannic acid, and ethylic and amylic acetates and valerianates. The specific gravity generally ranges between 0·9220 and 0·9040, corresponding to 48 and 56 per cent. of alcohol. The solid extract in whisky is usually below 1 per cent., and the total volatile acids under 0·1 per cent. In regard to the average composition of whisky, chemical literature furnishes but very meagre data. The examination of a large number of samples of ordinary American whisky in 1881, for the New York State Board of Health, gave the following results:—Specific gravity ranged from 0·9018 to 0·9645; alcohol (by weight) from 23·75 to 52·58; solid residue, from 0·100 to 0·752; ash, from 0·0020 to 0·0280. Several samples of rye whisky, examined by Mr. Green,[113] showed alcohol (by weight) from 32·50 to 51·20; tannic acid, 0·0003; acetic acid, 0·0012 to 0·002; sugar, 0·002 to 0·005; solid residue, 0·160 to 0·734.
Rum.—Rum is obtained by the distillation of the fermented juice of sugar-cane or of molasses; a very considerable proportion of the article bearing this name is, however, made from grain spirit. In France and Germany the mother-liquor remaining after the extraction of beet-sugar, is utilised in the manufacture of a spirituous liquor greatly resembling rum in properties. The characteristic odour and taste of the liquor are mainly due to the presence of ethylic butyrate, and are frequently factitiously communicated to its imitations by the direct addition of this ether or of butyric acid. Grain spirit is also sometimes treated with pineapples, which likewise impart the distinctive flavour. Rum is chiefly produced in the West Indies, and in North America. The specific gravity ranges from 0·874 to 0·926; alcohol, from 50 to 70 per cent.; solid residue, from 0·7 to 1·50 per cent; ash, under 0·10 per cent.[114]