300 FERMENTATION OF BEER. 



bined with both at higher temperatures, so as to 

 form acetic acid. 



Thus, then, this remarkable process of fermenta- 

 tion with the precipitation of a mucous-like ferment 

 consists of a simultaneous putrefaction and decay in 

 the same liquid. The sugar is in the state of 

 putrefaction, and the gluten in that of decay. 



Apperfs method of preserving food, and this 

 kind of fermentation of beer, depend on the same 

 principle. 



In the fermentation of beer after this manner, 

 all the substances capable of decay are separated 

 from it by means of an unrestrained access of air, 

 while the temperature is kept sufficiently low to 

 prevent the alcohol from combining with oxygen. 

 The removal of these substances diminishes the 

 tendency of the beer to become acescent, or in 

 other words, to suffer a further transformation. 



In Apperfs mode of preserving food, oxygen is 

 allowed to enter into combination with the sub- 

 stance of the food, at a temperature at which 

 decay, but neither putrefaction nor fermentation, 

 can take place. With the subsequent exclusion 

 of the oxygen and the completion of the decay, 

 every cause which could effect further decomposi- 

 tion of the food is removed. The conditions for 

 putrefaction are rendered insufficient in both cases ; 

 in the one by the removal of the substances sus- 

 ceptible of decay, in the other by the exclusion of 

 the oxygen which would effect it. 



