THE MANUFACTURE OF OTHER FERMENTED PRODUCTS 553 



and flavorless. It dries out very rapidly and is palatable only when 

 very fresh. 



In the common household method, a smaller amount of yeast is 

 mixed in a thin batter or sponge and allowed to multiply for ten to 

 eighteen hours. This batter is then thickened to a stiff dough and 

 allowed to rise until it doubles its volume. A second kneading is 

 then given and a little more flour added. After rising again for a few 

 hours it is baked. 



Bread made in this way is usually somewhat more open in texture, 

 not so white and with more flavor. It dries less rapidly and remains 

 palatable for two or three days. The difference seems to be due prin- 

 cipally to the action of bacteria on the gluten and other nitrogenous sub- 

 stances in the latter case. The bacterial action, however, is not 

 sufficient to give a perceptible acidity. 



Where leaven made from old dough is used, as in most parts of 

 Southern Europe, the part of bacteria in the fermentation is much 

 greater. 



The bread has a thicker and firmer crust, a fuUer flavor and a 

 distinct acidity which is often excessive. It holds its moisture well and 

 keeps for a week or longer. 



The making of so-called French bread, as it is carried out in Paris, is 

 a successful attempt to combine the good qualities of the above ex- 

 tremes and to avoid their defects. It is based on the fact that where 

 a leaven consisting of a mixture of yeast and bacteria is used, the yeast 

 develops more rapidly at the beginning and the bacteria at the end. 

 By successive additions of flour and aeration by repeated kneading, 

 sufficient yeast growth is obtained to make the bread light and the 

 bacteria kept within the limits necessary for flavor and keeping quali- 

 ties without causing undue acidity. 



Yeast as Food. — Enormous quantities of yeast are produced in 

 the various fermentation industries and thrown away as a waste prod- 

 uct after use. It has been calculated that over 60,000 tons of yeast 

 are produced by the breweries of Germany alone and nearly twice as 

 much by the distilleries. Recent tests have shown that this yeast 

 has a highly nutritive composition and can be used as a profitable 

 nitrogenous ration for all farm animals. By careful methods, a 

 human food can be prepared from it which is appetizing and nearly 

 three times as nutritious as beef. 



