The mashing process is different in very large distilleries, which have commodious mechanical appliances, and are prepared to mash vast amounts of material. It is customary to bring the corn mashed with water to the boil ing point by means of steam, and then to heat the corn to 300° to 310° F. (60 to 80 pounds pressure). The corn is kept at this tempera ture for 10 minutes in order to gelatinize the starch. The surplus steam is blown off, and the corn mash is cooled to about 164° F. At the same time, malt, rye, oats or barley is mashed in with water in a special mash tank, which is supplied with a simple agitator and a double copper attemperator coil. After both mashes are united, the temperature is about 130° F., which is the temperature at which the largest possible amount of sugar is formed.
This mashing method is used in the large factories both for the manufacture of whisky, high wines and spirits. The various brands of whisky are then made by the use of different materials of varying properties. These large distilleries also use slop in place of water when making a sour mash whisky. In order to ob tain a higher degree of acidification, more lactic acid is allowed to form in the malt mash. In comparing the large distilleries with the smaller ones, we find that while the latter can pay more attention to the characteristic properties of the whiskies, especially sour mash and fancy goods, the former does its practical work more techni cally and also obtains much higher yields. The manufacture of concentrated alcoholic spirits is only profitable when all the modern mechanical appliances are at hand, so that, owing to the constant decrease in the price of alcoholic spirits, the number of smaller plants is becom ing less.
Fermentation of the sugary mash is fermented in the fermenters by means of yeast. A very large number of different races of yeasts exist, each of which produces an alcoholic liquor differing in flavor from the others. They fall naturally into two classes: (1) Culture yeasts, and (2) wild yeasts. The former have been cultivated for long periods of time by the fermentation industries, and have acquired characteristics which render them of great value for the production of alcohol and alcoholic liquors. The yeast used in fermenting whisky mashes belongs to the genus sac charomyces cerevisice. The yeast used in fer menting wines from which brandy is distilled belongs to the genus saccharomyces ellzpsoideus.
The distiller's yeast must be able to flourish vigorously in solutions with a high percentage of acid, and also when the alcohol content of the mash becomes considerable. In England, com mon ale yeast is usually added; in France and Belgium either top-fermenting or compressed yeast, which is also used by bakers, is generally added. In the scientifically operated German distilleries, the inventions and discoveries of modern times are successfully used, as for in stance, a pure yeast culture of a distiller's yeast is made according to Hansen's method, just as a pure beer yeast is cultivated in many United States breweries according to the same method.
In the United States distilleries a yeast obtained by spontaneous fermentation is generally used. Here Delbrueck's teachings in regard to natural pure culture are of importance. Experience teaches that when several yeast species are present, a certain one can be developed under certain conditions of nourishment, because a mash of definite concentration and proportion of fermentable to non-fermentable substances, made from definite materials, consequently con taining definite percentages of albuminous and mineral substances, will vigorously develop at a definite temperature and acidity only one species of yeast and will suppress the rest. By main taining the same conditions on a larger scale, that is, by using a greater amount of mash, the yeast thus developed can be further propagated. But in spite of the utmost care, natural pure culture is oftentimes defective, because the standard requirements are not rigorously ob served. It may also happen that among the air yeasts which are developed for spontaneous fermentation, there is no species which will flourish under these requirements. Consequently, it would be advisable to introduce pure cultures, made from one indivdual cell, according to Hansen's method. Then the distiller would not be dependent on chance; and, of course, a pure yeast developed according to Hansen's method, would have to be cared for according to the principles of natural pure culture, as, otherwise, an infection with undesirable yeasts, mycoderma or fission fungi would gradually destroy the pure yeast.
In the United States distilleries the yeast is developed as follows: A clear malt mash is made from ground malt and pure water, generally distilled water. The water is boiled with hops, one ounce of hops per gallon of water, cooled to 170° F. and added to the ground malt, whereupon sacchari fication will take place. As soon as the conver sion is completed, a clear mash is drawn either by filtration or extraction, which is then con centrated to 18 to 30 per cent Balling and cooled to to 72° F. Air is forced into the mash in small copper vessels, so that after 24 to 48 hours the yeasts of the air will cause fer mentation. This mash in the copper jugs is the so-called stock-yeast and is cultivated as needed. In case the yeast thus obtained is not satisfac tory, the process is repeated. Most distillers constantly have a supply of this jug-yeast on hand and regenerate it by adding a portion of it to the above described, hopped, clear malt mash. This originalyeast is poured into sterilized cop per jugs and stored in an ice box or other suitably cool place.