348 FERMENTATION OF BEER. 



English, French, and most of the German beers, 

 are converted into vinegar when exposed to the 

 action of air. But this property is not possessed by 

 Bavarian beer, which may be kept in vessels only 

 half-filled without acidifying or experiencing any 

 change. This valuable quality is obtained for it by 

 a peculiar management of the fermentation of the 

 wort. The perfection of experimental knowledge 

 has here led to the solution of one of the most beau- 

 tiful problems of the theory of fermentation. 



Wort is proportionally richer in gluten than in 

 sugar, so that during its fermentation in the common 

 way, a great quantity of yeast is formed as a thick 

 scum. The carbonic acid evolved during the process 

 attaches itself to the particles of yeast, by which 

 they become specifically lighter than the liquid in 

 which they are formed, and rise to its surface. Glu- 

 ten in the act of oxidation comes in contact with 

 the particles of the decomposing sugar in the inte- 

 rior of the liquid. The carbonic acid from the sugar 

 and insoluble ferment from the gluten are disengaged 

 simultaneously, and cohere together. 



A great quantity of gluten remains dissolved in 

 the fermented liquid, even after the transformation 

 of the sugar is completed, and this gluten causes 

 the conversion of the alcohol into acetic acid, on 

 account of its strong disposition to attract oxygen, 

 and to undergo decay. Now, it is plain, that with 

 its separation, and that of all substances capable of 

 attracting oxygen, the beer would lose the property 

 of becoming acid. This end is completely attained 

 in the process of fermentation adopted in Bavaria. 



The wort, after having been treated with hops in 

 the usual manner, is thrown into very wide flat 

 vessels, in which a large surface of the liquid is 

 exposed to the air. The fermentation is then allowed 

 to proceed, while the temperature of the chambers 

 in which the vessels are placed is never allowed to 

 rise above from 45 to 50^ F. The fermentation lasts 

 from three to six weeks, and the carbonic acid 



