324 BEER, BAVARIAN 



Liebig, and much new light was thereby thrown upon this curious portion of vegetable 

 chemistry. 

 The following is a list of the principal beers brewed in Germany : 



1. Brown beer of Morseburg ; of pure barley malt. 



2. and beet-root sugar. 



3. barley malt, potatoes, and beet-root syrup. 



4. refined beet-root syrup alone. 



5. Covent or thin beer. 



6. Berlin white beer, or the champagne of the north. 



7. Broyhan, a famous Hanoverian beer. 



8. Double beer of Griinthal. 



9. Bavarian beer : 1. Summer beer; 2. Winter beer. 



10. Bock beer. 



11. Wheat Lager-beei (slowly fermented). 



12. White bitter beer of Erlangen. 



Considerable interest among men of science, in favour of the Bavarian beer process, 

 has been excited ever since the appearance of ' Liebig's Organic Chemistry.' In the 

 introduction to this admirable work, he says, ' The beers of England and France, and 

 ?or the most part those of Germany, become gradually sour by contact of air. This 

 defect does not belong to the beers of Bavaria, which may be preserved at pleasure in 

 half-full casks, as well as full ones, without alteration in the air. This precious 

 quality must be ascribed to a peculiar process employed for fermenting the wort, 

 called in German Untcrg'dhrung, or fermentation from below ; which has solved one of 

 the finest theoretical problems. 



' Wort is proportionally richer in soluble gluten than in sugar. When it is set to 

 ferment by the ordinary process, it evolves a large quantity of yeast, in the state of 

 a thick froth, with bubbles of carbonic acid gas attached to it, whereby it is floated to 

 the surface of the liquid. The phenomenon is easily explained. In the body of the 

 wort, alongside of-particles of sugar decomposing, there are particles of gluten being 

 oxidised at the same time, and enveloping, as it were, the former particles, whence 

 the carbonic acid of the sugar and the insoluble ferment from the gluten being simul- 

 taneously produced, should mutually adhere. When the metamorphosis of the sugar 

 is completed, there remains still a large quantity of gluten dissolved in the fermented 

 liquor, which gluten, in virtue of its tendency to appropriate oxygen, and to get 

 decomposed, induces also the transformation of the alcohol into acetic acid (vinegar). 

 But were all the matters susceptible of oxidisement as well as this vinegar ferment 

 removed, the beer would thereby lose its faculty of becoming sour. These conditions 

 are duly fulfilled in the process followed in Bavaria. 



'In that country the malt-wort is set to ferment in open backs, with an extensive 

 surface, and placed in cool cellars, having an atmospheric temperature not exceeding 

 8 or 10 C. (46 or 50 F.) The operation lasts from three to four weeks ; the car- 

 bonic acid is disengaged ; not in largo bubbles that burst on the surface of the liquid, 

 but in very small vesicles, like those of a mineral water, or of a liquor saturated 

 with carbonic acid, when the pressure is removed. The surface of the fermenting 

 wort is always in contact with the oxygen of the atmosphere, as it is hardly covered 

 with froth, and as all the yeast is deposited at the bottom of the back, under the form 

 of a very viscid sediment, called in German Unterhefe. 



' In order to form an exact idea of the difference between the processes of fer- 

 mentation, it must be borne in mind that the metamorphosis of gluten, and of azotised 

 bodies in general, is accomplished successively in two principal periods, and that it is 

 in the first that the gluten is transformed in the interior of the liquid into an insoluble 

 ferment, and that it separates alongside of the carbonic acid proceeding from the 

 sugar. This separation is the consequence of an absorption of oxygen. It is, how- 

 ever, hardly possible to decide if this oxygen comes from the sugar, from the water, 

 or even from an intestine change of the gluten itself; or, in other words, whether the 

 oxygen combines directly with the gluten, to give it a higher degree of oxidation, or 

 whether it lays hold of its hydrogen to form water. 



This oxidation of the gluten, from whichever cause, and the transformation of the 

 sugar into carbonic acid and alcohol, are two actions so correlated, that by an exclu- 

 sion of the one, the other is immediately stopped,' 



The superficial ferment (Oberhefe in German) which covers the surface of the fer- 

 menting works, is gluten oxidised in a state of putrefaction ; and the ferment of de- 

 posit is the gluten oxidised in a state of ercmacausis, or slow combustion. 



The surface yeast, or barm, excites in liquids containing sugar and gluten the 

 same alteration which itself is undergoing, whereby the sugar and the gluten suffer 

 a rapid and tumultuous metamorphosis. Wo may form an exact idea of the different 



