this change depends on the quantity of water employed, and the degree of heat adopted in the operation.
Inasmuch as barley germinates very readily, and develops a larger proportion of diastase than any other grain, except wheat, it is generally used as a producer of diastase. Barley germinated according to proper methods is called malt. and its preparation is fully described in Chapter VI.
There are many methods of preparing grain for fermentation, but all use at least two of the following operations :—grinding, gelatinizing, steeping, or steaming, mashing saccharifying.
Grinding. Where cookers or the Henze steamers are not used every form of grain should be crushed or ground into a coarse flour. This is in order that the starchy interior may be easily acted on by the diastase. If the grain is not to be mixed with malt later it must be ground more finely so that it may be thoroughly penetrated by the water. The grains should not be ground except as required, as ground grain is liable to heating and consequent loss of fermentability, and is also liable to become musty, in which condition it loses much of its fermentability.
Steeping. This operation is best carried on in vats or tanks of iron or cement, for the reason that wood absorbs impurities, which are communicated to the grain, thus lessening its germinative power. Wooden vats should be thoroughly scrubbed after use, and be kept continually whitewashed. The steeping tub should hold about two-thirds more than the amount of ground grain to be steeped.
Steeping is affected by pouring on to the crushed grain hot and cold water in such quantity that after 10 minutes or so of brewing the mixture will have a temperature of 75° to 95°F.
This warmth makes the water more penetrating. The water should not be poured in all at once, but a little at a time, until the grain is covered to a depth of three or four inches. Care should be taken not to let the temperature get too high, not above 95°F., as a temperature above that point kills the germinating power.
The mixture of crushed grain and water is now stirred for 10 minutes and then left to subside for half an hour. It is then stirred again and the mixture left to steep for 30 or 40 hours, depending on the temperature of the atmosphere, the dryness of the grain, and the character of the water. In very warm weather the water should be changed every few hours by running it off through a hole in the bottom of the tub and running in fresh at the top. This prevents fermentation setting in prematurely.
When the grain swells, and yields readily between the fingers it has been sufficiently steeped, and the water is run off. This is an old method of gelatinizing grain, but a better is by the use of cookers or high pressure steamers as described for potatoes.
Mashing. This consists in mixing the coarse flour with malt and then by means of certain operations and mechanisms bringing it to a condition most favorable to fermentation through the action of yeast. The mixing of the raw flour with barley or other malt effects the conversion of the starch of the grain into maltose. The yeast afterwards converts this maltose into sugar.
Saccharifying. To effect the action of the diastase of the malt on the grain, in the old methods, boiling water must bepoured into the vat until the temperatureof the mass reaches about 140° to 168°F., the whole being well stirred meanwhile; when this temperature has been reached, the vat is again covered and left to stand for four hours, during which time the temperature should, if possible, be maintained at 140°F.., and on no account suffered to fall below 122°F., in order to avoid the inevitable loss of alcohol consequent upon the acidity always produced by so low a temperature. In cold weather the heat should of course be considerably greater than in hot. It should be also remarked that the greater the quantity of water employed, the more complete will be the saccharification, and the shorter the time occupied by the process.
Having undergone all the above processes, the wash is next drawn from the mash tub into a cistern, and from this it is pumped into the coolers. When the wash has acquired the correct temperature ,viz., from 68° to 78°F., according to the bulk operated upon, it is run down again into the fermenting vats situated on the floor beneath. Ten to twelve pints of liquid or 5^ to 6^ lbs. of dry brewer's yeast are then added for every 220 lbs. of grain; the vat is securely covered, and the contents are left to ferment. The process is complete at the end of four or five days, and if conducted under favorable conditions there should be a yield of about 11 gallons of pure alcohol to every 220 lbs. of grain employed.
There are a number of different methods of mashing, having each its advantages, and applicable to particular varieties of grain.
We will first consider the mashing of the steeped grain in general by one of the older and simpler processes.
The grain to be mashed, which has been ground and steeped as before described, is mixed with malt in the proportion of four to one or even eight to one. In addition, three or four pounds of chaff to every hundred or so pounds of steeped grain should be used.
Mash. Water is then run into the mash tub in the proportion of about 600 gallons to each 60 bushels of grain. Its temperature should be between 120° and 150°F. During the entrance of water, the mass is well stirred so as to cause the whole of the grain to be thoroughly soaked and to prevent the formation of lumps. It is best to add the grain to the water gradually and to stir thoroughly.
To this mass about 400 gallons of boiling water is gradually added to keep the temperature at about 145°F. During the addition of the boiling water the mash should be continually stirred so that the action of the water shall be uniform. This operation should last about two and one half hours. The vat should be then covered and left to stand from three-quarters to one hour for saccharification.
Another method of saceharifying is to turn boiling water gradually into the mash tank until the mixture has acquired a temperature of from 140° to 180°F. The mass is thoroughly stirred, and the tub is covered and left to subside for from two to four hours, during which time the temperature should not be allowed to fall below 120°F. A small tub needs more heat than a larger tub, and more heat is required in winter than in summer.
A convenient method of regulating the temperature of the mash tank, would be by a coil of pipes on tile bottom. This would be connected by a two-way cock to a steam boiler and to a source of cold water. Heat should never be carried over 180°F., and the best temperature is from 145° to 165°F.
The greatest effect of the diastase of the malt upon the gelatinized starch is at 131°F. For ungelatinized starch this is not great enough, hence the greater part of tile mashing is carried on at the lower temperature and only towards the end should the temperature be raised to thc maximum 150°F.
Every distiller uses his own judgment as to the amount of the mashing water used, its temperature, the length of time during which the mash rests, and the length of time for saccharification.
Saccharification may be recognized by the following signs: The mash loses its first white mealy look, and changes to dark brown. It also becomes thin and easily stirred. The taste is sweet and its-odor is like that of fresh bread.
Corn and other grain may be mashed conveniently in such an apparatus as that described on page l0, as used for potatoes the steam being introduced under pressure.
The water is first placed in the steamer. Steam is introduced into the water and it is brought to a boil The corn is then introduced gradually, the steam pressure increased to its maximum, and the mass blown out as described in Chapter VII. Hellefreund's apparatus (see page 118) may also be used with ground corn.
The corn or grain not previously crushed or ground is introduced into a steamer in the proportion of 200 lbs. of corn to 40 gallons of water. The steamer should have about 100 gallons of steam space for this amount.
The mashes described above are thick, more or less troublesome to distil, and only simple stills can be used. By the following method a clear saccharine fluid or wort can be obtained.
A mash vat is used having a double bottom. The upper bottom is perforated and between the two bottoms is a draw-off pipe and a pipe for the inlet of water.
Upon the upper perforated bottom is first placed a layer of between two and three pounds of chaff. Upon this is turned in a mixture of 400 lbs. corn and malt in the proportions of / malt to 4/5 grain. Eighty-seven gallons of water at a temperature of from 85° to 105°F. is then let in to the bottom, while the mixture is thoroughly agitated for 10 minutes. It is then left to subside for half an hour.
After this steeping process, the mass is again agitated while 175 gallons of water at 190°F. are let into the tub while the mass is continually and thoroughly stirred by mechanical stirrers. Brewing lasts for half an hour, and the liquid is then left to stand for seven hours.
At the end of this period the grain is covered by clear liquid which is drained off through the draw-off cock into the fermenting back.
To the contents left in the steeping tank 135 gallons of boiling water are added as before and the liquid therefrom drawn into the fermenting back.
It usually requires three infusions, to extract the whole of the saccharine and fermentiscible matters contained in the grain. In some places, it is customary to boil down the liquors from the three mashings until they have acquired a specific gravity of about 1.05, the liquor from a fourth mashing being used to bring the whole to the correct degree for fermentation, the liquors from the third and fourth being boiled down to the same density and then added to the rest. In a large Glasgow distillery, the charge for the mash tubs is 29,120 lbs. of grain together with the proper proportion of malt. Two mashings are employed, about 28,300 gallons of water being required; the first mashing has a temperature of 140°F., and the second that of 176°F. In Dublin the proportion of malt employed is only about one-eighth of the entire charge. One mashing is employed, and the temperature of the water is kept at about 143°F. The subsequent mashings are kept for the next day's brewing.
By this process the grain is entirely deprived of all fermentible substances which have been carried away in a state of liquid sugar.
The whole operation of preparing and saccharifying grain is to-day carried on in steamers, such as described on page 11, and cooking apparatus such as shown in Fig. 1, or in the Henze high pressure steamers and preparatory mash vats described in Chapter II.
In steaming grain without, pressure, the finely crushed grain is poured slowly into a vat previously nearly filled with water at a temperature of about 140 degrees F. A little less than half a gallon of water is used for each pound of grain. Care must be taken to stir the mass constantly to prevent lumping. When all the corn is mixed in, steam is allowed to enter and the temperature raised to about 200 degrees F. It should be left at this temperature for an hour, or an hour and a half, when the temperature is reduced to 140°F. when about 10 per cent. of crushed malt is added and the temperature reduced to 68°F. by means of suitable cooling devices.
When steam cookers are used, the cylindrical boiler is first filled to the proper degree with water at a temperature of 140°F. The meal is then let in gradually being constantly stirred the while. The boiler is then closed and steam gradually let in while the mass is stirred until a pressure of 60 pounds and a temperature of 300°F. has been reached. The starch then becomes entirely gelatinized, the pressure is relieved, and the temperature reduced to 212°F. and then rapidly brought to 145°F. The malt is added mixed with cold water, at such a stage before the saeccharifying temperature is reached that the cold malt and water will bring it to 145°F. The malt is stirred and mixed with the mash for five or ten minutes and the mixed mass let into a drop tub when saccharification is completed. It is then cooled as described.
When the Henze steamers are used the grain may be treated in either the whole grain or crushed, as the high pressure to which it is subjected and the "blowing out" act to entirely disintegrate it. In this mode of operation, water is first let into the steamer and brought to a boil by the admission of steam. The grain is then slowly let into the apparatus. The water and grain should fill the steamer about two thirds full. The steamer is left open and steam circulated through the grain and water for about an hour, but without any raising of pressure. This acts to thoroughly cook and soften the grain.
When sufficiently softened the steam escape cock in the upper part of the steamer (see Fig. 2) is regulated to allow a partial flow of steam through it and a greater flow of steam is admitted though the lower inlet. This keeps the grain in constant ebullition under a pressure of 30 lbs. or so. After another period of an hour the pressure in the steamer is raised to 60 lbs. at which point it is kept for half an hour, when the maximum steam pressure is applied, and the greater portion of the disintegrated mass blown out into a preparatory mass tub, into which malt has been placed mixed with water. The blowing out should be so performed that the temperature in the mass in the tubs shall not exceed 130°F. The mass is stirred and cooled and then the remainder of the mass in the steamer admitted to the tub which should bring the temperature of the mass up to 145°F. It is kept at this temperature for a period varying from half an hour to one and one-half hours and is then cooled to the proper fermenting temperature.
Another method of softening corn so that its starch is easily acted upon by the diastase of the malt is to steep it in a sulphurous acid solution at a temperature of about 120°F. for from fifteen to twenty hours. The mass is then diluted to form a semi-liquid pulp and heated to about
190°F. for an hour or two during which the mass is constantly stirred. The malt is then added, the mass is saccharified, cooled and then fermented.
Another method is to place mixed grain and hot water in a cooker of the Bohn variety (Fig. 45). After half an hour of stirring and cooking under ordinary pressure, the steam pressure is raised to 45 lbs. This is kept up for from two to three hours when the grain is reduced to a paste. Concentrated muriatic acid equal to 2^ per cent of the weight of grain is then forced in, under steam pressure. In half an hour the grain will be entirely saccharified and ready for fermenting.
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