BAVARIAN BEER. 181 



to the liquor, oxidation commences, and it begins to 

 pass into the acetous fermentation(47 6). 



435. For the same reason, also, when a cask has 

 once been tapped, it should be used at once ; the 

 liquor is brisk at first, being charged with carbonic 

 acid, which renders it pleasant to the taste, and pre- 

 serves it from further change ; ere long the carbonic 

 acid escapes, the liquor becomes flat, then the oxygen 

 of the air begins to act upon it, and it soon turns 

 sour. 



436. Malt liquor, which has once become clear and 

 fit for use, must never be shaken ; as ferment is 

 always formed and deposited, even during the very 

 slow fermentation which takes place in the cask : 

 agitation not only renders the liquor thick and 

 turbid by difiusing the spent ferment throughout it, 

 but is very likely to induce a fresh fermentation, 

 which would probably pass into the acetous one. 



437. In the Bavarian mode of brewing, the fer- 

 mentation of the wort is allowed to proceed very 

 slowly, exposed to a low temperature in large open 

 vessels. Though slow, this fermentation is very 

 complete, the whole of the ferment is deposited at 

 the bottom of the vat, whilst very little rises to its 

 surface, and there is hardly any frothing of the wort. 

 Beer thus made has very little tendency to enter 

 into a new state of fermentation, even by the action 

 of the air. 



438. BREAD-making depends in great part on fer- 

 mentation ; a small quantity of sugar which exists in 



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