CHEMISTRY OF BAKING 



27 



used in making "light" bread. It would require such a 

 large quantity of it to raise the dough that it would be 

 much more expensive than yeast. The taste of biscuits 

 baked in a few minutes after mixing the dough is quite 

 different from the taste of bread which has been given 

 several hours for the dough to rise. This difference 

 in the taste of " light" bread and biscuits is due to 

 three things, i. Growth of the yeast plant takes place 

 in the dough. 2. The wheat grain has a ferment in it 



called diastase. This dia- , ; . 



stase is in the flour made 

 from wheat, and it changes 

 some of the starch in the 

 flour to sugar while the 

 bread is rising. It takes 

 several hours for the dia- 

 stase to change much of 

 the starch to sugar, and 

 so it does not have time 

 to act in the quickly made 

 biscuits. 3. Heat changes 

 starch to dextrin sugar, but 

 it must have time to do so. The heat has a longer time 

 to act on the large loaf than it does on the small biscuit. 

 22. Yeast. Yeast is a plant so small that a good 

 microscope is necessary to see it. It consists of only 

 one cell. The plant grows by each cell dividing into two 

 unequal parts. The smaller part is called a bud while 

 attached to the larger part. When a yeast plant does 

 not have food enough, it grows a tough protective cover- 

 ing over itself, and then can dry sufficiently to be carried 

 by the wind with the dust and float about in the air. 

 On this account the air is full of yeast plants, but they are 



YEAST PLANTS 

 (Magnified.) 



