In 200 liters of water at 125 degrees F., 100 kg. of the grains are mixed and constantly stirred for thirty minutes, until all lumps have disappeared, the temperature in the meantime remaining constant. At this temperature the dissolving of the albuminous matters of the grains is favored, and the changing of the starches into sugar and dextrin is facilitated.
Saccharification of the Mash.—At the expiration of the thirty minutes the temperature of the mash is gradually increased by steam from 122 to 158 degrees F., and constantly stirred.
It has been substantiated that these temperatures are best suited for a perfect gelatinization and saccharification of the starches without injuring the diastasic properties of the malt. At the same time, a temperature of 158 degrees F., which is continued for two hours, is useful to effectually sterilize the mash by destroying the undesirable bacteria. During this time the diastase, which, as we have seen, was produced in the sprouting barley during malting, effects its function in the quickest possible manner. The result is a very sweet, lasting fluid.
In order to ascertain whether the saccharification has been complete, a small portion of the mash is filtered and tested with a drop of tincture of iodine. When the tincture of iodine discontinues to produce a blue coloring in the filtered fluid the saccharification is complete.
Acidulation of the Mash.—This is probably the most momentous stage of compressed yeast manufacturing, and watchfulness must be practiced, if the object be to produce a pure yeast free from all possible contamination.
The means used for this purpose is the introduction of lactic acid fermentation. The mash is covered up, occasionally the mash is stirred, but always from bottom upward, so as to bring as large a surface as possible in contact with the atmosphere (oxygen), while the mash is kept at a temperature favorable to lactic ferment growth.
The reason for this acidulation is twofold. In the first place, the lactic ferments assist in converting the insoluble albuminous matters of the grains into soluble matter. Technically, this is known as changing the albuminoids into peptones.