350 FERMENTATION OF BEER. 



Yeast of this kind is oxidized gluten in a state of 

 putrefaction^ and by virtue of this state it induces 

 a similar transformation in the elements of the sup-ar. 



The yeast formed during the fermentation of Ba- 

 varian beer is oxidized gluten in a state of decay. 

 The process of decomposition which its constituents 

 are suffering, gives rise to a very protracted putre- 

 faction (^fermentation) in the sugar. The intensity 

 of the action is diminished in so great a degree, 

 that the gluten which the fluid still holds in solution 

 takes no part in it ; the sugar in fermentation does 

 not excite a similar state in the gluten. 



But the contact of the already decaying and pre- 

 cipitated gluten or yeast, causes the eremacausis of 

 the gluten dissolved in the wort; oxygen gas is 

 absorbed from the air, and all the gluten in solution 

 is deposited as yeast. 



The ordinary frothy yeast may be removed from 

 fermenting beer by filtration, without the fermenta- 

 tion being thereby arrested ; but precipitated yeast 

 of Bavarian beer cannot be removed without the 

 whole process of its fermentation being interrupted. 

 The beer ceases to ferment altogether, or, if the 

 temperature is raised, undergoes the ordinary fer- 

 mentation. 



The precipitated yeast does not excite ordinary 

 fermentation, and consequently is quite unfitted for 

 the purpose of baking ; but the common frothy yeast 

 can cause the kind of fermentation by which the 

 former kind of yeast is produced. 



When common yeast is added to wort at a tem- 

 perature of between 40^ and 45° F., a slow tranquil 

 fermentation takes place, and a matter is deposited 

 on the bottom of the vessel, which may be employed 

 to excite new fermentation ; and when the same 

 operation is repeated several times in succession, 

 the ordinary fermentation changes into that process 

 by which only precipitated yeast is formed. The 

 yeast now deposited has lost the property of excit- 



