FERMENTING POWER OF DIFFERENT YEASTS 77 



of them will raise bread, but some of them are poorly 

 adapted to this purpose. Some of them, like brewer's 

 yeast, act so slowly 

 that the bread will not 

 rise rapidly enough. 

 The use of yeast 

 in bread making is 

 dependent entirely 

 upon its fermenta- 

 tive power, and con- 

 sequently the value 

 of any type of yeast 

 will depend upon 

 the energy of its 

 fermentation. Some 

 types of yeast pro- 

 duce a more vigor- FIG. 38. 

 ous fermentation 

 than others. The 

 cake of compressed 

 yeast, for example, 

 produces a more vig- 

 or ous fermentation 

 in bread than either the brewer's yeast or the dried cake. 

 The relative value of the three types in fermenting flour 

 is shown in Fig. 38. In each tube was placed a mixture 

 of flour and water so as to fill completely the closed arm 

 on the right. Each was then inoculated with a different 

 yeast, the same quantity in each. As they fermented 

 the sugar in the flour, the gas given off collected in the 

 closed arm as shown, and the vigor of the fermentation 



Three fermentation tubes inocu- 

 lated with different varieties of yeast, show- 

 ing the differences in fermenting power, as 

 indicated by the amount of gas collected in 

 the closed tube. The tube on the right was 

 inoculated with dried yeast, the middle tube 

 with brewer's yeast, and the left-hand tube 

 with compressed or distillery yeast. 



