354 FERMENTATION 



' If a beer deprived of all the gorms of disease is prepared, and wort that lias not 

 undergone any change is then added, a beer is obtained, in all cases, that -will bo per- 

 fectly healthy and free from any living organisms excepting those which constitute tho 

 globules of the alcoholic yeast. This experiment proves the correlation that exists 

 between tho changes in beer and microscopical organisms. 



'From my studies on wine I have deduced that wine is not a liquid th;it changes 

 of itself ; the same thing is true of boor. Tho causes of tho changes come from v, it h- 

 out. Tho only modifications that are spontaneous are the changes of a chemical order, 

 sometimes from contact with oxygon, or from the effects of growing old, and a reaction 

 taking place between the constituent elements. 



'These changes in the nature of a liquid have nothing to do with disease. AVhen 

 any change takes place in beer, such as becoming thin, putrid, sour, strange organisms 

 are developed in it, and these organisms would not be there unless the germs had 

 existed originally in the liquid mass. Beer might bo carried into tho hottest eountries 

 if these germs of disease did not exist in it. 



4 Nothing can better demonstrate that the changes in the wort of beer are duo to 

 microscopical organisms, than the fact that if this wort has been previously boiled, or 

 any other means used to destroy the germs of vitality, no change whatever takes place 

 when the wort is brought into contact with the air. 



4 Concerning the yeast of beer, tho facts do not present themselves with such sim- 

 plicity as when dealing with the wort or the beer. The latter are dead substances ; 

 the yeast, on the contrary, is living. Very skilful botanists, amongst whom arc M. 

 Turpin, M. Hoffmann, and M. Trecul, have arrived at the conclusion from their own 

 observations, that the yeast of beer gives birth to different mildews, amongst others 

 the Penicillium glaucum. 



1 It is well known that the yeast of beer is liable to great changes, and these changes 

 are always accompanied by the development of microscopical organisms. From whenc.- 

 do these organic productions come ? Are they a modification of the cellules of the 

 yeast in the conditions of the new life, or do the organisms find their origin in the 

 dust from the objects with which the yeast has been in contact? 



* I prepared some yeast deprived of all germs foreign to its own nature, and I can 

 therefore give an account of the changes it underwent when brought in contact with 'the 

 pure air. In this condition the yeast appeared perfectly inert, like a mineral sub- 

 stance, giving rise to no fermentation whatever ; it did not even give birth to the 

 Mycoderma mni, which is so like the yeast in its structure, its form, and mode of 

 development. 



' If one understands the preceding principles, it is easy to see that beer, which is no 

 longer exposed to changes, may be made at any temperature. 



' We must consider, first, that the beer is forced to come to a state of ebulli- 

 tion when it is still in the form of extract of malt with hops ; during this process 

 all the germs of disease are . destroyed. The hot wort is enclosed in a vat, and 

 then cooled either by contact with the air or by a current of water. The germs can bo 

 easily kept out during the process of cooling, by allowing carbonic acid gas to outd- 

 one of the tubes, while the other tube allows the excess of gas to escape. It must 

 then be put to the operation of fermentation, as much as possible sheltered from the 

 common air, and using a yeast that is perfectly pure. Where is this pure j'east to bo 

 found ? 



'I have observed that even in the best breweries tho yeasts are always impuiv, 

 because this impurity is due to the processes now in use. The employment of impure! 

 yeast renders the making of beer in closed vessels impossible, and even exaggerates 

 the defects of tho present process, if closed vessels are employed. 



' The physiological difference between yeast and the sick fermentation is worthy of 

 attention. While the yeast of beer lives and multiplies in contact with tho air more 

 rapidly than in the presence of carbonic acid gas, the germs of disease, on tho contrary, 

 are cramped in their life by the presence of oxygen gas. The result is, when tho 

 operations are carried on, sheltered from the air, the accessory fermentations develop 

 with facility, while the alcoholic fermentation is slackened, because tho yeast 

 cannot spread in contact with tho oxygen a new source of activity. All the attempts 

 to make beer in closed vessels have failed up to tho present time. But thes.- 

 arise from the impurity of the yeast commonly used by brewers. For it' tl; 

 does not contain germs foreign to its nature, they can bather appear spontaneously nor 

 by a transformation in the yeast . Such are the principal motives for tho employment 

 of a pure yeast, especially in my process. Several methods can bo employed 

 production of pure yeast, but it would take too long to explain the means I have 

 adopted; it will suffice to say that the difference ot the action of tho oxygon of the 

 air on the yeast ,-nd on the sil-k !' rim-tat im should bi- profited by. 



4 1 put then into the wort pure yeast ; the fermentation t akes place, and being efl 



