356 FERMENTATION OF BEER. 



has a very important influence on the quantity of 

 alcohol generated. It has been mentioned, that the 

 juice of beet-roots allowed to ferment at from 86^ to 

 950 (30^ to 350 C.) yields no alcohol; and that 

 afterwards, in the place of the sugar, mannite, a 

 substance incapable of fermentation, and containing 

 very little oxygen, is found, together with lactic acid 

 and mucilage. The formation of these products di- 

 minishes in proportion as the temperature is lower. 

 But in vegetable juices, containing nitrogen, it is 

 impossible to fix a limit, where the transformation 

 of the sugar is undisturbed by any other process of 

 decomposition. 



It is known, that in the fermentation of Bavarian 

 beer, the action of the oxygen of the air, and the 

 low temperature, cause complete transformation of 

 the sugar into alcohol ; the cause which would pre- 

 vent that result, namely, the extraction of the oxy- 

 gen of part of the sugar by the gluten, in its con- 

 version into ferment, being avoided by the introduc- 

 tion of oxygen from without. 



The quantity of matters in the act of transforma- 

 tion is naturally greatest at the beginning of the 

 fermentation of must and wort ; and all the phenom- 

 ena which accompany the process, such as evolution 

 of gas, and heat, are best observed at that time. 

 These signs of the changes proceeding in the fluid 

 diminish when the greater part of the sugar has 

 undergone decomposition ; but they must cease en- 

 tirely before the process can be regarded as com- 

 pleted. 



The less rapid process of decomposition which 

 succeeds the violent evolution of gas, continues in 

 wine and beer until the sugar has completely dis- 

 appeared; and hence it is observed, that the specific 

 gravity of the liquid diminishes during many months. 

 This slow fermentation, in most cases, resembles the 

 fermentation of Bavarian beer, the transformation 

 of the dissolved sugar being in part the result of a 

 slow and continued decomposition of the precipita- 



