YEAST FROM BEER AND WINE. 339 



in a new solution of sugar, and which has in conse- 

 quence received the name of ferment. 



The alcohol and carbonic acid are produced from 

 the elements of the sugar, and the ferment from those 

 azotized constituents of the grape-juice, which have 

 been termed gluten, or vegetable albumen. 



According to the experiments of De Saussure, 

 fresh impure gluten evolved, in five weeks, twenty- 

 eight times its volume of a gas which consisted | of 

 carbonic acid, and \ of pure hydrogen gas ; ammo- 

 niacal salts of several organic acids were formed at 

 the same time. Water must, therefore, be decom- 

 posed during the putrefaction of gluten ; the oxygen 

 of this water must enter into combination with some 

 of its constituents, whilst hydrogen is liberated, a 

 circumstance which happens only in decompositions 

 of the most energetic kind. Neither ferment nor 

 any substance similar to it is formed in this case ; 

 and we have seen that in the fermentation of sac- 

 charine vegetable juices, no escape of hydrogen gas 

 takes place. 



It is evident, that the decomposition which gluten 

 suffers in an isolated state, and that which it under- 

 goes when dissolved in a vegetable juice, belong to 

 two different kinds of transformations. There is 

 reason to believe, that its change to the insoluble 

 state depends upon an absorption of oxygen, for its 

 separation in this state may be effected, under cer- 

 tain conditions, by free exposure to the air, without 

 the presence of fermenting sugar. It is known also 

 that the juice of grapes, or vegetable juices in gen- 

 eral, become turbid when in contact with air, before 

 fermentation commences; and this turbidness is owing 

 to the formation of an insoluble precipitate of the 

 same nature as ferment. 



From the phenomena which have been observed 

 during the fermentation of wort,* it is known with 



* Wort is an infusion of malt ; it consists of the soluble parts of this 

 substance dissolved in water. — Ed. 



