THE FARMER'S MAGAZliNE. 



35 



the subatance fermcuted is mall;, ia which the starch that the 

 grain contains has by incipieut vcg;etation been couverted into 

 sugar, and thus rendered fermentable. 



lu the acctou'j feruieatation tiie raatorials employed are 

 similar to those used for the vinous, but the temperature em- 

 ployed is higher. Little acetous acid ia produced unless almo- 

 spheric air is present, the oxygen of which must combine 

 directly with the requisite proportion of oxygen and carbon 

 that constitute acetic acid. But as alcohol may be converted 

 into vinegar, p.a indeed ia practised in wins countries, it is pos- 

 sible, even when sugar is produced from malt, that the previous 

 formation of alcohol may occur. And this view will beat ex- 

 plain what happens, and show that by the mere absorption of 

 oxygen, so as to form water, and without the evolution of any 

 carbonic acid, acetic acid may be formed. 



With respect to the putrefactive fermentation, it is to be 

 observed that it is spontaneous decaj' and decomposition of 

 vegetable and animal matter, which is unaccompanied with 

 the production of alcohol or acetic acid. In the vegetable 

 putrefactive fermentation, the principal product is carbonic 

 acid, and probably water ; both derived from the combina- 

 tion and .ibsorption of the oxygen of the air, which unites 

 with the hydrogen and carbon of the vegetable matter. In 

 the putrefactive fermentation of animal matter ammonia 

 is a very usual product, owing to the presence of azote, 

 which enters largelj' into the composition of animal matter 

 in general ; and thus, by uniting with the hydrogen, the 

 alkali just mentioned is produced. 



BREAD-MAKING, 



When flour is made into a paste with water, the mixture 

 is called dough; and when this is suffered to remain in a 

 moderately warm place, it undergoes that partial and spon- 

 taneous decomposition which is called fermentation, and 

 which, in order to distinguish it from other kinds, has been 

 called, but without sufJicient reason for the distinction, the 

 panary fermentation. During this fermentation, a portion 

 of the carbon and oxygen of partially-decomposed flour 

 recombines, so as to form what is sometimes called fixed 

 air, but correctly carhonic acid gas. This, during its 

 natural tendencj' to escape into the air, is arrested in its 

 progress throui;h the dough by the adhesiveness of the 

 gluten, and forms, owing to its retentiou, numerous cavities 

 in it. It is thus that wheat-flour makes lighter bread than 

 that of oats or rye, owing to the larger quantity of gluttn 

 it contains, by which the bread is rendered more porous 

 and lighter, and consequently more digestible. 



This plan of fermentation would, however, not only require 

 much time, but dough thus spontaneously fermented ia never 

 quite free from putrescence and acid, both of which are in- 

 jurious to the flavour of the bread. To remedy these incon- 

 veniences, the process was foimerly accelerated by adding to 

 a mass of recesit dough a quantity of old dough in a state of 

 strong fermentation : this was called leaven, and the mass to 

 which it was added was said to be leavened. 



Although tlie use of leaven was an unquestionable improve- 

 ment, a still further one was made by the employment of yeast 

 instead of it : by this, the fermentation is much more rapidly 

 and perfectly effected. Tne exact nature of this ferment has 

 not been ascertained ; it is the frothy scum that rises on the 

 surface of bter during its fermentation : it is a very com- 

 pounded substance, and it is by no means determined to what 

 portions of it the fermentive power is particularly owing. It 

 appears to contain gluten, but that alone is not sufficient to 

 account for the effects produced, as it is jncapable of ferraeu- 

 tatioa per se. 



When the baker proceeds to the preparation of dou.ih by 

 meai;s of the yeast fermentation, he at first takes generally a 

 portion only, but sometimes the whole, of tlie water wanted to 

 make the requisite quantity of dough. In this water, which 

 varies in temperature, according to circumstances, from 90 to 

 100 de.;rees, there is dissolved a certain portion of salt; but 

 less than that which will finally be required, in order to 

 comminiicate the necessary fl.ivour to the bread. Yeast is 

 now mixed with the water, and then a portion of flour ia 

 added, which is al^^ays less than the quantity to be ultimately 

 employed in forming the finished dough. The mixture is next 

 covered up, aud set apart in a warm situation; within an hour 

 after which, signs of commencing decomposition make their 

 appearance. The substance thus placed apart is termed, ia 

 the language of the bake-house, Vatspowje : its formation and 

 abandonment to spontaneous decomposition is termed setting 

 the sponge, aud according to the relation which the amount of 

 Mater iu the sponge bears to the whole quantity to be u?ed iu 

 the dough, it is called quarter, half, or whole sponge. The 

 sponge begins to swell out and heave up, evidently in conse- 

 quence of the generation of some internal elastic fluid, which 

 iu th's instance is always carbonic acid gas. If the sponge be 

 of a semi-liquid consistence, large air bubbles soon force their 

 way to the surface, when they break, and dissipate in rapid 

 succession. But when the sponge posaessea the cousiateuce 

 of thin doitgh, it conflaes this gaseous substance within it, until 

 it dilates e|uahly and progressively to nearly double its ori- 

 ginal volume, when, uo longer containing the pent-up air, it 

 bursts, and subsides. This process of rising aud falling suc- 

 ceasively might be actively carried on, and frequently re- 

 peated, during twenty-four hours ; but experience has taught 

 the baker to guard against allowing full scope to the energy 

 of the fermentative principle. He generally interferes after 

 the first, or at farthest after the second or third dropping of 

 the sponge; and, were he to omit this, the bread formed from 

 his dough would invariably prove sour to both taste and 

 smell. He therefore, at this period, adds to the sponge 

 the remaining portion of flour, water, and salt neces- 

 sary to form the dough of the required consistence 

 and size, and next incorporates all these materials with 

 the sponge by a long and laborious course of kneading. 

 When this process has been continued until the fermenting 

 and the newly-added flour have been intimately blended toge- 

 ther, and until the glutinous parts of the flour are wrought to 

 s.;ch a union and consistence, that the dough, now tough and 

 elastic, will receive the smart pressure ef the hand without ad- 

 hering to it when withdrawn, the kneading ia for a while sus- 

 pended. The dough is left to itself for a few hours, during 

 which time it is iu a state of active fermentation, now diffused 

 through its whole extent. After the lapse of thia time it is 

 subjected to a second, but much less laborious, kneading, the 

 object of which is to distribute the gas engendered within it 

 as equably as possible throughout its entire constitution, so 

 that uo part of the dough may form a sod or ill-raise 1 bread, 

 from the deficiency of this carbonic-acid gaa on the one hand, 

 or a too vesicular or spongy bread on the other. 



After the second kneading, the dough is weighed out into 

 the portions requisite to form the kinds of bread desired, which 

 are once more set aside for an hour or two in a warm place. 

 The continuance of fermentation soon generates a sufficient 

 quantity of fresh carbonic acid gas within them to expand each 

 mass to about double its former volume. They are finally 

 baked into loaves, which, when they quit the oven, have at- 

 tained a size nearly twice as bulky as that at which they 

 entered it. It should be remarked that the generation of the 



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