566 MICROBIOLOGY OF FOODS 



knead the rising dough, "proof" the loaves, and bake the bread within 

 a regular schedule of eight hours or less. 



Mixing of the ingredients must be thorough to insure uniform 

 fermentation throughout the dough. Mixing also results in the inclu- 

 sion of air with the dough which stimulates yeast growth and activity. 

 During the rising of the dough several changes take place. Carbon 

 dioxide is formed and distends the dough by the formation of small 

 bubbles of gas held by the gluten of the flour. Wheat flour is the only 

 one possessing enough gluten to permit of this phenomenon. The 

 proteins of the flour are to some extent peptonized by proteolytic 

 enzymes of the flour, thus tending to reduce the harsh 'texture of the 

 raw dough. Diastase is active to a slight extent and also tends to 

 soften the texture of the dough. Lactic and other bacteria develop 

 to an extent depending largely upon the time and upon the original 

 number of such organisms present. Contrary to popular belief, lactic 

 organisms are not the ones usually responsible for the "sour taste ' : 

 of some breads, this undesirable flavor is usually due to butyric acid 

 organisms. 



Ordinarily the dough is allowed to rise in shallow wooden troughs 

 in the dough mixing room. After it has risen sufficiently it is "cut 

 down" and rekneaded. Often the cutting and rekneading are again 

 repeated before the bread is molded. The cutting down prevents the 

 bread rising too rapidly and permits a sufficiently long period of rising 

 to insure the proper flavor and texture, and the frequent kneading 

 results in the formation of a loaf of more uniform texture. Too much 

 yeast causes the dough to develop large gas pockets or gas may escape 

 from the dough from large bubbles, resulting in the breaking and slacken- 

 ing of the dough. Too little yeast results in too slow a fermentation 

 with consequent increase in danger from growth of undesirable organisms. 

 The dough from the dough or "proof room goes to mechanical 

 molding machines which form the dough into loaves of the desired 

 weight and deliver them to the proof box where the loaves are subjected 

 to a temperature favorable to rapid fermentation. They may or may 

 not be rekneaded before baking. 



Baking is in many large plants accomplished in "traveling ovens' 1 

 in which the loaves traverse the oven on heavy metallic conveyors, 

 thus resulting in a great saving of labor and in standardization of 

 baking time. The ovens are electrically controlled by thermo-regula- 



