This yeast is propagated for use in this way: The distiller first heats a rye and malt mash very rapidly to F., when the maximum saccharifying action takes place, and keeps it at this temperature a short time. Then the heat is raised quickly to 144° when the maximum liquefaction of starch takes place. Finally the heat is raised to 150° to 154°, which destroys harmful bacteria, but does not injure diastase if plenty of sugar is present in the solution. The temperature most favorable to the action of distiller's yeast is between 75° and 81°. A slightly acid wort favors the development of distiller's yeasts, and checks the brewery yeasts and bacteria.
Souring is accomplished through a special mash at 148° to 158°, from kilned malt to which is added unmalted wheat, corn or rye. This mash at 122° is inoculated with a pure culture of lactic acid bacteria. When about 1 per cent of lactic acid has been formed, the temper ature is raised to 165° and the lactic bacteria killed. The mash is then cooled to 80° and pitched with distillery yeast, and then slowly cooled to As fermentation proceeds the temperature rises, but it must be kept below 85°. This yeast mash is ripe in 10 to 14 hours after pitching, and is then run into the sweet wort at 68°. The period of greatest fermentation is after 24 hours, and continues 12 to 18 hours during which the temperature is kept below 85° to prevent loss of alcohol through evaporation. The duration of fermentation is for spirits and sweet-mash whiskies, 72 hours, while for sour mash whisky it requires 76 hours.
Sometimes abnormal conditions arise, among which is the so-called "foaming fermentation.° that is an exceptionally stormy fermentation, in which losses of alcohol occur, due to the flowing over of the mash over the edge or rim of the fermenter. This is a result of various defects, and is either partly due to the materials, or the yeast, or may be occasioned by irregularities in the operation, or even by other causes. It would lead too far to enumerate them here, but much has been written on this subject by ex perts.
The fermented mash, called the sour mash, is now pumped into the distilling apparatus, where it is distilled as is fully described in the article DISTILLATION. It is customary to distil the whiskies to 102-105 proof and spirits to 188-190 proof. In small distilleries an ordinary pot still is used for whiskies and a liquor of about 70 proof is obtained, which is concentrated to 101-102 proof in a doubler. A doubler consists of a copper cylinder having a wide outlet pipe, from which the vapors enter the condenser. In
the small distilleries, the heating is accomplished by direct firing, by which a peculiar, characteris tic taste, which is appreciated by the consumers, is engendered. Such whisky is called "Fire Copper Bourbon Whisky.° When oats, barley or wheat are used in the manufacture of certain whiskies, they are worked up in the same manner as rye in the above-described mash.
Potatoes are not mashed in the United States, although they are commonly used in Germany. They contain only 18 to 20 per cent of starch, while the cereals contain 60 and more per cent of starch. Instead of mashing the ground, rasped or chipped potatoes in open mash-tubs, as was formerly done and is even done to-day in small plants, they are now first steamed under a pressure of two to three atmospheres, whereby the starch is put in condition to be easily acted upon by the diastase. After the steaming the potato mass is cooled to 55 to 60° C. (131 to 140° F.), which is the best saccharification tem perature. Then this mass is mixed with malt, generally green malt, either in the cooker or in the mash-tub, and saccharified. It is customary in Germany to make a thick mash of 22 per cent (Balling), sometimes even of 26 to 28 per cent The fermentation is accomplished by the addition of a cultivated pure culture yeast. The distilling process is similar to our method. In Germany less brandy but more highly con centrated alcohol for industrial purposes is made.
In all those cases, in which a mealy sub stance is utilized, the thin slop remains after the distillation, which contains all the ingredients of the corn and yeast mash. Besides the skins and husks, we find albumen, unfermented sugar, lactic acid, acetic acid, glycerine, mineral sub stances, etc. This Wet slop was mainly used as feed for cattle, so that formerly every distiller also had a herd of cattle. It is claimed that an animal's health will suffer if slops are copiously fed, so that on this account, and especially in order to dispense with some of the labor caused by the maintenance of the cattle, the slop was dried. By thorough drying, which can be done immediately after the distillation, spoiling is prevented and a constantly durable and valuable article of commerce, which need never be given away below its full value, is obtained. The drying of slop is accomplished in several opera tions: (1) Settling of the insoluble substances; (2) Pressing out; (3) Drying in cylindrical driers.