326 FERMENTATION OF BEER. 



action of the oxygen of the air, and the low temperature, cause 

 complete transformation of the sugar into alcohol ; the cause 

 which would prevent that result, namely, the attraction of the 

 gluten for oxygen, by combining with which it is converted into 

 ferment, being exercised on oxygen derived from without. 



The quantity of matters in the act of transformation is na- 

 turally greatest at the beginning of the fermentation of must and 

 wort ; and all the phenomena which accompany the process, 

 such as evolution of gas, and heat, are most distinct 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 entirely before the process can be regarded 

 as completed. 



The less rapid process of decomposition which succeeds the 

 violent evolution of gas, continues in wine and beer until the 

 sugar has completely disappeared ; 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 decomposi- 

 tion of the precipitated yeast ; but a complete separation of the 

 azotized substances dissolved in it cannot take place when air is 

 excluded.* 



Neither alcohol alone, nor hops, no* indeed both together, pre- 

 serve beer from becoming acid. The better kinds of ale and 

 porter in England are protected from acidity, but at the loss of 

 the interest of an immense capital. They are placed in large 

 closed wooden vessels, the surfaces of which are covered with 

 sand. In these they are allowed to lie for several years, so that 



* The great influence which a rational management of fermentation has 

 npon the quality of beer, is well known in several of the German states. 

 In the grand-duchy of Hesse, for example, a considerable premium is 

 offered for the preparation of beer according to the Bavarian method; and 

 the premium is to be adjudged to any one who can prove that the beer 

 brewed by him has lain for six months in the store-vats without becoming 

 acid. Hundreds of casks of beer became changed to vinegar before an em- 

 pirical knowledge of those conditions was obtained, the influence of which' 

 is rendered intelligible by theory 



