56 THE WONDERFUL HOUSE THAT JACK HAS 



large amount of starch and ease of digestion make it so 

 valuable that in China and Japan it is the principal 

 food. 



Let us consider something that is really very curious 

 about the common, everyday process of bread making. 

 Yeast, which is commonly used to make bread dough 

 rise, is made up of very tiny plants that are closely 

 related to bacteria. When these yeast plants are 

 placed in the dough, they increase rapidly, and, uniting 

 with the sugar, produce carbonic acid gas and alcohol. 

 The gas in attempting to escape raises the dough, 

 making it light, and the alcohol evaporates. Yeast 

 grows best in a temperature of from seventy to ninety 

 degrees, the higher being desirable in winter, because 

 of the coldness of the flour. 



If the yeast is allowed to grow too long or at too 

 high a temperature, it acquires a sour flavor. The 

 number of hours allowed bread to rise depends upon 

 the temperature, from five to ten being the usual 

 number. The oven should be hot when the dough 

 is placed within, in order that the yeast plant may 

 be quickly destroyed. Afterward the heat should be 

 reduced, and the bread kept in long enough to be 

 thoroughly baked. 



Baking powders are used instead of yeast in making 

 biscuit and similar preparations. These powders con- 

 tain mineral substances, which, when united with 

 water and flour, form carbonic acid gas that raises .the 

 dough. If yeast or something similar were not used 



