FERMENTATION.

465

through a canvass bag, and freed from the superfluous moisture by squeezing. The bagwith its doughy mass must next be surrounded with dry ashes, to remove the remaininghumidity, and to arrest any further fermentation. This consistent ferment may be usedinstead of beer yeast.

It is difficult to prepare an artificial yeast without barm. The best process for thisPurpose is the following. Take five parts of honey, one part of powdered tartar, andsixteen parts of wheat or barley malt, stir the whole in water of the temperature of 12.2°F., and place in a fermenting heat; when the yeast will, as usual, be eliminated.

The change which gluten or vegetable albumen undergoes in the different kinds oftneal, when it becomes a ferment, consists apparently in an oxydation, since analysisshows that this ferment contains more oxygen than gluten does.

It has been already stated that yeast in its liquid condition readily putrefies, andbecomes altogether useless for the process of fermentation. In order to preserve it fors °me time, it must be dried to such a degree as to resist spontaneous decompositionwithout losing its fermentative faculty; but completely dried yeast loses that property,a "d does not recover it by being again moistened. Beer barm may be dried after beingWashed several times with cold water, till the last quantity comes off clear; but the in-?^luble portion must be allowed to settle"fully before the water is poured away from it.I he residuum being freed as much as possible from water, by drainage and pressurebetween flannel cloths, is to be dried in the shade by a current of warm air as quicklyas Possible, with the aid of frequent turning over. It must be afterwards kept in dryea rthen vessels. Yeast may also be preserved a short time in activity by being kneaded'T it h as much barley or wheat flour as it can take up without losing the doughy con-Sls tence. Dried yeast has, however, always an impaired activity. The easiest and most? er tain method of preserving yeast in its primitive power, is by mixing it, after pressurej ri flannel, with as much pulverized sugar as will render it dry, and putting up the mix-are in air-tight vessels. The fermentative power of yeast is destroyed by the followinghteans: 1. as already stated, by making it completely dry either by the evaporation ofhe water, or its abstraction by alcohol; 2. by boiling, which if continued for ten minutese aders yeast quite inoperative; 3. by the action of such substances as dissolve out itsEssential constituents; by alkalis, for instance, since the particles of yeast seem to beParative only in their insoluble granular state; 4. by such substances as form combina-°ts with it, and thereby either alter its nature, or at least increase the cohesion of itshPstituent parts, so that they can no longer operate upon sweet liquors by the decompo-a g affinity of its ultimate particles. Such bodies are the acids, especially the mineral

es > tannin and most salts, particularly the metallic, which unite with the yeast into new.“'Pounds. The volatile oils which contain sulphur exercise the same paralyzing influ-

ence

Th,

hpon yeast.

c °nf circumstances wfl'ch promote, and are necessary to, the vinous fermentation are,of °J'. nia bly to the above views, the following:—1. The presence of the proper quantityf er ctlve yeast, and its proper distribution through the worts. If in the course of a slacktfi e entat i°n the yeast subsides to the bottom, the intestine motions cease entirely, buters^ 111 ^ exeiled anew by stirring up the ingredients, or rousing the tun, as the brew-thore^M, A cer I a ' n degree of warmth, which, should never be less than 51° F., norc 0m taan 86°; the temperature of from 68° to 77° being the most propitious for thethe r ei ? a ? mea t and progress of fermentation. When other circumstances are the same,So tlwu^ ^ le fermentation is proportional to the temperature within certain limits,pr 0c * , 7 l° we ring it, the action may be moderated at pleasure. 3. The fermentation°n a c Ps l * le ' 5etter and more equably the greater the mass of fermenting liquor, probablya etiv P ° Unt . 0 ^ t * le uniformly high temperature, as well as the uniform distribution of theSa ccha^ artlC * es tlle yeast b y the greater energy of the intestine movements. 4. Theit wifi tl<le s °i u tion must be sufficiently diluted with water; when too much concentratedPosed su”* ^ erment - Hence very sweet musts furnish wines containing much undecom-tn ten „ ’ ar ‘ For a complete fermentative action, one part of sugar should be dissolvedFer parts °f wa ter.

iho Perat . ntatlo » may be tempered or stopped: 1. by those means which render the yeastIfle sulpha 6 ’ particularl y by the oils that contain sulphur, as oil of mustard ; as also byl Ae ferine t° U,S atu * su ' p A ur ' c acids. The operation of the sulphurous acid in obstructinge Aminati 0 n & f° n °*" must consists partly, no doubt, in its absorbing oxygen, whereby the>e Powerf ,K he yeaSt Z Parlicles is prevented. The sulphurous acid, moreover, actsPhuric: acid* f’! pon fomenting liquors that contain tartar, as grape juice, than sulSets th e vp» decomposes the tartdric salts, and, combining with their bases,

sulphurous ap'n 6 aC * 1 * ^ r6e ’ W A' C A does not interfere with the fermentation; but the' f 'th the «],* opera tes direetjyupon the yeast: 2. by the separation of the yeast, eithergating ma ,„ i r ”7 subsidence : 3. by lowering the temperature to 45° F. If the fer-1 "dll not CC ; >:n,! meat at this temperature, and be drawn off from the subsided yeast,1 terment again, though it should be he:

30

■ heated to the proper pitch.