BEER, BAVARIAN 325 



states of these two kinds of yeast by comparing the superficial to vegetable matters 

 putrefying at the bottom of a marsh, and the bottom yeast to the rotting of wood 

 in a state of eremacausis. The peculiar condition of the elements of tho sediment 

 ferment causes them to act upon the elements of the sugar in an extremely slow 

 manner, and excites the change into alcohol and carbonic acid, without affecting the 

 dissolved gluten. 



If to wort at a temperature of from 46 to 60 P. the top yeast be added, a quiet 

 slow fermentation is produced, but one accompanied with a rising-up of tho mass, 

 while yeast collects both at the surface and bottom of the backs. If this deposit be 

 removed to make use of it in other operations, it acquires by little and little the cha- 

 racters of tho Unterhefe, and becomes incapable of exciting the phenomena of the first 

 fermenting period, causing only, at 59 P., those of the second, namely, sedimentary 

 fermentation. It must be carefully observed that the right Unterhefe is not the pre- 

 cipitate which falls to the bottom of backs in the ordinary fermentation of beer, but 

 is a matter entirely different. Peculiar pains must be taken to get it genuine, and in 

 a proper condition at the commencement. Hence the brewers of Hesse and Prussia, 

 who wished to make Bavarian beer, found it more to their interest to send for the 

 article to Wurzburg, or Bamberg, in Bavaria, than to prepare it themselves. When 

 once the due primary fermentation has been established and well regulated in a 

 brewery, abundance of the true Unterhefe may be obtained for all future operations. 



In a wort made to ferment at a low temperature with deposit only, the presence of 

 tho Unterhefe is the first condition essential to tho metamorphosis "of the saccharum, 

 but it is not competent to bring about the oxidation of the gluten dissolved in the 

 wort, and its transformation into an insoluble state. This change must 'be accom- 

 plished at the cost of the atmospherical oxygen. 



In the tendency of soluble gluten to absorb oxygen, and in the free access of. the 

 air, all tho conditions necessary for its eremacausis are to bo found. It is known that 

 the presence of oxygen and soluble gluten are also the conditions of acetification 

 (vinegar-making), but they are not the only ones ; for this process requires a tem- 

 perature of a certain elevation for the alcohol to experience this slow combustion. 

 Hence by excluding that temperature, the combustion (oxidation) of alcohol is ob- 

 structed, while the gluten alone combines with the oxygen of the air. This property 

 does not belong to alcohol at a low temperature, so that during the oxidation in this 

 case of the gluten, the alcohol exists alongside of it, in the same condition as the gluten 

 alongside of sulphurous acid in the muted wines. In wines not impregnated with the 

 fumes of burning sulphur, the oxygen which would have combined at the same time 

 with the gluten and the alcohol does not seize either of them in wines which have 

 been subjected to mutism, but it unites itself to the sulphurous acid to convert it into 

 the sulphuric. The action called sedimentary fermentation is therefore merely a 

 simultaneous metamorphosis of putrefaction and slow combustion ; the sugar and the 

 Unterhefe putrefy, and the soluble gluten gets oxidised, not at the expense of tho 

 oxygen of the water and the sugar, but of the oxygen of the air, and the gluten then 

 falls in the insoluble state. The process of Appert for the preservation of provisions is 

 founded upon the same principle as the Bavarian process of fermentation, in which all 

 the putrescible matters are separated by the intervention of the air at a temperature 

 too low for the alcohol to become oxidised. By removing them in this way, the 

 tendency of the beer to grow sour, or to suffer a further change, is prevented. 

 Appert's method consists in placing, in presence of vegetables or meat which we wish 

 to- preserve, the oxygen at a high temperature, so as to produce slow combustion, but 

 without putrefaction or even fermentation. By removing the residuary oxygen after 

 the combustion is finished, all the causes of an ulterior change are removed. In tho 

 sedimentary fermentation of beer, we remove the matter which experiences the com- 

 bustion ; whereas, on the contrary, in tho method of Appert, we remove that which 

 produces it. 



The temperature at which fermentation is carried on has a very marked influence 

 upon the quantity of alcohol produced. It is known that the juice of beets set to 

 ferment between 86 and 95 P., does not yield alcohol, and its sugar is replaced by a 

 less oxygenated substance, mannite, and lactic acid, resulting from the mucilage. In 

 proportion as the temperature is lowered the mannite fermentation diminishes. As 

 to azotisod juices, however, it is hardly possible to define the conditions under which 

 the transformation of the sugar will take place, without being accompanied with 

 another decomposition which modifies its products. The fermentation of beer by 

 deposit demonstrates that by the simultaneous action of the oxygen of the air and 

 a low temperature, the metamorphosis of sugar is effected in a complete manner ; 

 for the vessels in which tho operation is carried on are so disposed that the oxygen 

 of the air may act upon a surface great enough to transform all the gluten into 

 insoluble yeast, and thus to present to tho sugar a matter constantly undergoing de- 



