392 ORGANIC CHEMISTRY. 



Holds yeast 98 2. PRODUCTION OF YEAST. - Yeast has 



produced? no t on jy fa e p Ower o f converting sugar 

 into alcohol, but it at the same time occasions the 

 production of more yeast from dissolved protein. In 

 the ordinary process of beer brewing, the newly formed 

 yeast collects on the surface of the fermenting vats. 

 It is thence removed, to serve as the excitant of a new 

 fermentation, or to be employed in the production of 

 bread, which is, chemically considered, an analogous 

 process. 



983. DIFFERENT KINDS OF FERMENTA- 



Mention seve- 



ral kinds of TioN. The products of fermentation are 

 fermentation. Different, according to temperature and 

 other circumstances. Thus the same sugar which at 

 40, to 86, with cheese used as a ferment, yields car- 

 bonic acid and alcohol, at a temperature of 86, to 95 

 is converted into lactic acid. The latter, by the further 

 action of the curd, with slight elevation of tempera- 

 ture, is converted into butyric and carbonic acids. By 

 the same ferment, at a still higher temperature, a portion 

 of gum is produced with the lactic acid. These diffe- 

 rent processes of transformation have received, respec- 

 tively, the names of the vinous, lactic, butyric, and 

 viscous fermentations. The conversion of starch into 

 sugar by diastase may be regarded as a species of fer- 

 mentation. This substance is a slightly changed glu- 

 ten. It is always produced in germination, and may 

 be precipitated by alcohol in the form of white flakes, 

 from a concentrated infusion of malt. One part of it 

 is sufficient to convert two thousand parts of starch 

 into sugar. 



