BREAD 199 



The alcoholic liquid is sprinkled on the surface in such 

 a way that it will be evenly distributed over the shavings, 

 which soon become covered with bacterial growth. The 

 fermentative process produces heat, and hence there is a 

 constant current of air through the holes at the bottom of 

 the cask. The air passes upward through the shavings and 

 out at the top. In this manner the bacteria are provided 

 with an abundant supply of air facilitating the oxidation 

 process. As fresh food is constantly supplied and as the 

 by-products of the fermentation are also constantly re- 

 moved, the change goes on continuously and with rapidity. 



It is essential that the alcoholic solution does not contain 

 too much nitrogenous food, since this would so accelerate 

 the growth of bacteria as to fill the interstices with bacteria 

 and cause a consequent reduction of the flow of air through 

 the shavings. It is essential that the mass of bacterial 

 growth be kept in a healthy and active condition, so that 

 the cells shall exert their oxidizing action rapidly. Usually 

 the liquid is passed through a series of three tanks situated 

 one above the other. By the time it flows from the last 

 tank, the oxidation will be sufficiently complete. 



Bread. The making of bread represents another fer- 

 mentation industry that is carried out in many homes. If 

 flour, water, a small amount of salt, and fat, such as lard 

 or butter, are mixed and baked, a dense hard mass is ob- 

 tained, such as a cracker or unleavened bread. If, however, 

 yeast is added to the mixture, and the dough placed under 

 conditions that permit the yeast to grow, the sugar is 

 changed into alcohol and carbon-dioxide. The dough made 

 from such flours as wheat contains gluten, which imparts 

 a plasticity to the mass. As the gas is formed, it is unable 

 to escape readity from the dough, and the whole mass 

 "rises," producing the "sponge" which characterizes all 

 leavened breads. When the gas is heated in the baking 



