beer perfectly clear. These conditions existing, the principal fermentation is completed. THE YEAST CROP. When the beer is ripe for tanking (racking on Ruh), the beer should be drawn or pumped from the fermenting vat, avoiding all agitation, as the yeast has a tendency to rise by the escape of carbonic acid gas under the yeast. The quantity and soundness of the yeast crop are largely influenced by operations during the progress of fermentation. In the beginning the matter in suspension in the wort, composed mainly of proteids, will partly settle and partly gather at the surface in the fermenting tub. In order to obtain the yeast as free as possible from this suspended matter, hop-resin and other substances like hop-resin that appear in the Kräusen: I. Skim off the dark head after the appearance of Kräusen, or run the beer into another vat as soon as in Kräusen. 2. Remove the dark particles of hop-resin from the Kräusen while the latter are falling back. 3. Skim off the cover before racking on storage ("Ruh"). The bulk of the yeast will be found settled on the bottom. The top, which is darker from admixtures of hop-resin, is apt to contain more light yeast, and small cell types, like wild yeast, if present in the beer at all, are found in greater quantities in the top layer. This dark layer should be skimmed off. The middle layer will be found to be lightest in color, and this part only should be preserved for future fermentations, leaving the bottom stratum, which again has a deeper color, and, having been first deposited, contains larger quantities of old, dead, and weak yeast cells, to go among the refuse. The middle layer which is conveyed to a yeast tub, may be at once refreshed and developed for pitching or left standing without watering for a few days if properly kept cool by "swimmers," or attemperator pipes, not by ice directly, since ice may contain impurities. The yeast may also be watered, which is preferably done the day before using. Next morning the surface water with the yeast particles floating on it is drained off, and the ycast refreshed and developed as for a new fermentation. The new yeast crop should be most carefully examined before being used again, and if found in any way unsound or contaminated, should be treated as directed under the respective heads. FERMENTATION PHENOMENA EXPLAINED. The fermentation phenomena may be explained as follows: As soon as the yeast is stirred into the wort it begins to split up the sugar into alcohol and carbonic acid, thereby developing heat, in consequence of which the temperature of the fermenting liquid rises, and the indication of the saccharometer becomes lower as the sugar is decomposed. The carbonic acid escapes, with the exception of about 5 per cent, which remains in the beer, part of the escaping gas raising the head of Kräusen. This escaping gas carries to the surface all the flocculent particles in suspension, like the coagulated albuminoids, giving rise, in the first stages of fermentation, to the thick, dark cover of scum. The hop-resin, which is held in solution chiefly by the sugar, becomes less soluble as the sugar decreases, and is carried, together with coagulated albumen, to the surface of the beer, where it discolors the Kräusen, or settles on the bottom, discoloring the yeast. The yeast multiplies during fermentation, is kept suspended by the escaping carbonic acid gas, and thus gives the beer a somewhat reddish appearance. The activity of the yeast increases up to the high Kräusen period, then gradually settles, and as fermentation draws to a close the beer appears darker in the vat. When the head collapses, there is comparatively little sugar left in the wort. Hence, the saccharometer falls with increasing rapidity up to the collapse of the head, and the temperature rises, whereas, after that time, the saccharometer falls more slowly, and the temperature decreases, owing to the atmosphere of the fermenting room being about 41° F. (4° R.) and cooling the liquid more rapidly than the diminishing activity of the yeast serves to heat it, even without the use of attemperators. The higher the temperature, and the larger the quantity of yeast in the beer, the quicker will the sugar ferment, the quicker will the temperature rise, the quicker will the saccharometer fall, the quicker carbonic acid will develop, the higher will the Kräusen rise. The fall of the saccharometer indication, according to Balling, is called "apparent attenuation," and the percentage of this fall, the "apparent degree of attenuation." The indication of the saccharometer itself at the end of the fermentation period is called the "apparent extract of beer." Taken together with the original gravity of the wort, the apparent attenuation enables the calculation of the percentage of alcohol, from which, in turn, is determined the real attenuation, the "real degree of attenuation," and the Balling of beer. (See "Figuring in the Brewery.") The consistency of the Kräusen head is due largely to the viscousness of the albuminoids by which the high volutes of foam are held together, to collapse after the generation of carbonic acid has fallen below the amount necessary to support the foam. The yeast does not ferment all the sugar in the wort, but leaves an average of 1.5 per cent after the principal fermentation, of which about one-half pcr cent is maltose and one per cent malto-dextrin. (See "Bottom Yeast.") HIGHER PITCHING TEMPERATURES. The wort, upon reaching the starting tub, always contains foreign germs which it took up on the surface and Baudelot coolers. Before fermentation starts, these foreign germs will multiply with comparative rapidity, and after fermentation has started, are suppressed the more effectively, the more quickly fermentation reaches the high Kräusen stage, at which the fermenting action of the yeast is at its height, as is the temperature of the fermenting liquid. The old practice is to cool the wort to 42° F. (4.5° R.) and to allow hours to pass before pitching, sometimes waiting over night. This is not in accordance with scientific principles, and, consequently, Wahl, on the occasion of a convention of the United States Brewmasters' Association, held at Baltimore, proprosed the following treatment for use in American breweries: Refresh and develop the yeast with first wort of 59° F. (12° R.) and put in the starting tub, timing this preparation so that the mass is just beginning to ferment at the moment when the first wort reaches the starting tub from the Baudelot cooler. The wort should run on the yeast, instead of the yeast being put into the wort. The wort is cooled down to 49° F. (7.5° R.) instead of 40-42° F. (3.5-4.5° R.). When in Kräusen-which will be in 20 to 24 hours instead of 40 to 45 as by the old practice-pump the wort into another vat or distribute among the fermenters. The temperature will have reached 51° F. (8.5° R.) by this time. Keep it at this height by means of "swimmers," or attemperators until the Kräusen have fallen down sufficiently, and cool in about three days down to 39° F. (3° R.), working so that the decrease of the saccharometer in the last 24 hours will not exceed 0.1 per cent. The advantages of this practice are many: 1. The wort need not be cooled down so low, that is, refrigeration is saved. 2. The wort is ready for pitching sooner. 3. Fermentation sets in sooner. 4. Fermentation is finished 2 to 4 days earlier. 5. The development of the yeast is more vigorous. 6. The yeast remains purer. 7. Less Kräusen are needed, their temperature being higher; or, equal amounts of Kräusen do more work and give more life to the beer in a shorter time than colder Kräusen. The new practice has met with a speedy recognition, having been introduced with good results in many breweries. Fermentation of a wort pitched at high temperature: Thermometer in de-) 49 51 51 51 51 51 grees F. and R... 85 Saccharometer in per cent.. 13.0 12.0 8.5 8.5 8.5 8.5 10.75 9.25 7.75 6.2 3 4 51 48 £5 42 39 3 5 BOTTOM YEAST. (See also Yeasts and Fermentation.) The substance, by the agency of which fermentation is carried on is called yeast. The course of the fermentation as performed by the yeast depends not only on the vitality and environment of the yeast, as age of yeast, temperature, aëration, composition of nutritive medium, presence or absence of other organisms, but also upon the type of yeast employed. Types of cultivated yeast are distinguished by differences in the following properties possessed, or effects produced, by them: 1. Degree of attenuation; 2. Fermentative energy, or rapidity of attenuation; 3. Reproductive energy, or growth of yeast; 4. Rapidity of settling of yeast, or clarification of beer; 5. Qualities of beer obtained, as taste, odor, and durability. (See "Yeasts and Fermentation.") The closest attention should be devoted to the yeast, as only by a sound, that is, pure and strong, yeast can a sound beer be produced. CHARACTERISTICS OF A GOOD BOTTOM YEAST. It has a thick, stiff, pasty consistency, not watery or slimy, a yellow to brownish color, a bitter taste due to hop-resin, and a characteristic odor. It consists, for the most part, of single cell organisms of the class saccharomyces and species cerevisiæ. Yeast mechanically encloses a large amount of water, or beer-about 20 per cent through which are dispersed minute bubbles of carbonic acid gas, that escapes when the yeast is stirred, emitting a rustling sound. After the beer has run from the fermenter, the yeast sediment should be quite firm and thick. However, unless an absolutely pure culture, every yeast has an admixture of foreign organisms, as bacteria, wild yeasts, and mycoderma. these impurities may be classified as "potentially dangerous." Since wild yeast or mycoderma cells do not settle so readily as culture yeast, the different layers of yeast in a fermenting vat will not be found generally to contain wild yeast or mycoderma in uniform numbers. Nor is the brewer safe in judging from the absence of wild yeast or mycoderma in the yeast sediment that All |