FERMENTATION OF BEER 



109 



compounds of hydrogen are known which 

 form hydrates ; and custom, which rejects 

 all dissimilarity until the claim to peculiarity 

 is quite proved, leads us to prefer an opinion, 

 for which there is no farther foundation than 

 that of analogy. The woad (Isatis tinctoria) 

 and several species of the Nerium contain a 

 substance similar in many respects to gluten, 

 which is deposited as indigo blue, when an 

 aqueous infusion of the dried leaves is ex- 

 posed to the action of the air. Now it is 

 very doubtful whether the blue insoluble in- 

 digo is an oxide of the colourless soluble 

 indigo, or the latter a combination of hydro- 

 gen with the indigo blue. Dumas has found 

 the same elements in both, except that the 

 soluble compound contained 1 equivalent of 

 hydrogen more than the blue. 



In the same manner the soluble gluten 

 may be considered a compound of hydrogen, 

 which becomes ferment by losing a certain 

 quantity of this element when exposed to 

 the action of the oxygen of the air under fa- 

 vourable circumstances. At all events, it is 

 certain that oxygen is the cause of the in- 

 soluble condition of gluten; for yeast is not 

 deposited on keeping wine, or during the 

 fermentation of Bavarian beer, unless oxy- 

 gen has access to the fluid. 



Now whatever be the form in which the 

 oxygen unites with the gluten whether it 

 combines directly with it or extracts a por- 

 tion of its hydrogen, forming water the 

 products formed in the interior of the liquid, 

 in consequence of the conversion of the glu- 

 ten into ferment, will still be the same. Let 

 us suppose that gluten is a compound of an- 

 other substance with hydrogen, then this 

 hydrogen must be removed during the ordi- 

 nary fermentation of must and wort, by 

 combining with oxygen, exactly as in the 

 conversion of alcohol into aldehyd by ere- 

 macausis. 



In both cases the atmosphere is excluded; 

 the oxygen cannot, then, be derived from 

 the air, neither can it be supplied by the 

 elements of water, for it is impossible to sup- 

 pose that the oxygen will separate from the 

 hydrogen of water, for the purpose of unit- 

 ing with the hydrogen of gluten, in order 

 again to form water. The oxygen must, 

 therefore, be obtained from the elements of 

 sugar, a portion of which substance must, 

 hi order to the formation of ferment, undergo 

 a different decomposition from that which 

 produces alcohol. Hence a certain part of 

 the sugar will not be converted into carbonic 

 acid and alcohol, but will yield other pro- 

 ducts containing less oxygen than sugar it- 

 self contains. These pfoducts, as has already 

 been mentioned, are the cause of the great 

 difference in the qualities of fermented li- 

 quids, and particularly in the quantity of 

 alcohol which they contain. 



Must and wort do not, therefore, in ordi- 

 nary fermentation, yield alcohol in propor- 

 tion to the quantity of sugar which they 

 hold in solut m, a part of the sugar being 

 employed in the conversion of gluten into 1 



ferment, and not in the formation of alcohol. 

 But in the fermentation of Bavarian beer all 

 the sugar is expended in the production of 

 alcohol; and this is especially the case when- 

 ever the transformation of the sugar is not 

 accompanied by the formation of yeast. 



It is quite certain that in the distilleries of 

 brandy from potatoes, where no yeast is 

 formed, or only a quantity corresponding to 

 the malt which has been added, the propor- 

 tion of alcohol and carbonic acid obtained 

 during the fermentation of the mash corre- 

 sponds exactly to that of the carbon contained 

 in the starch. It is also known that the 

 volume of carbonic acid evolved during the 

 fermentation of beet-roots gives no exact in- 

 dication of the proportion of sugar contained 

 in them, for less carbonic acid is obtained 

 than the same quantity of pure sugar would 

 yield. 



Beer obtained by the mode of fermenta- 

 tion adopted in Bavaria contains more alco- 

 hol, and possesses more intoxicating proper- 

 ties, than that made by the ordinary method 

 of fermentation, when the quantities of 

 malt used are the same. The strong taste 

 of the former beer is generally ascribed to its 

 containing carbonic acid in larger quantity, 

 and in a state of more intimate combination j 

 but this opinion is erroneous. Both kinds 

 of beer are, at the conclusion of the fermen- 

 tation, completely saturated with carbonic 

 acid, the one as much as the other. Like 

 all other liquids, they both must retain such 

 a portion of the carbonic acid evolved as 

 corresponds to their power of solution, that 

 is, to their volumes. 



The temperature of the fluid during fer 

 mentation has a very important influence 

 on the quantity of alcohol generated. It 

 has been mentioned, that the juice of beet- 

 roots allowed to ferment at from 86 to 95 

 (30 to 35 C.) yields no alcohol; and that 

 afterwards, in the place of the sugar, man- 

 nite, a substance incapable of fermentation, 

 and containing very little oxygen, is found, 

 together with lactic acid and mucilage. The 

 formation of these product? diminishes in 

 proportion as the temperature is lower. But 

 in vegetable juices, containing nitrogen, it is 

 impossible to fix a limit, where the trans- 

 formation of the sugar is undisturbed by 

 any other process of decomposition. 



It is known that in the fermentation of 

 Bavarian beer the 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 extraction of the oxygen 

 of part of the sugar by the gluten, in its 

 conversion into ferment, being avoided by 

 the introduction of oxygen from without. 



The quantity of matters in the act of 

 transformation is naturally greatest at the 

 beginning of the fermentation of must and 

 wort; and all the phenomena which accom- 

 pany the process, such as evolution of gas, 

 and heat, are best observed at that time. 

 These signs of the changes proceeding in 



