SOUR BREAD 93 



to be produced by bacteria. Since the acids are caused 

 by bacteria, this subject really belongs to a later division 

 of our discussion ; but its close relation to bread making 

 leads to its introduction at this point. 



Recognizing that the cause of sour bread is due to 

 the growth of bacteria, it is not difficult to suggest the 

 proper means of avoiding it. Fresh yeasts only should 

 be employed. A good quality of flour should be used, and 

 the dough should be mixed in clean utensils. After mix- 

 ing, the dough should be placed in a clean dish at a proper 

 temperature (75 in summer, 90 in winter), so that the 

 bread will rise in about eight hours. Dough should never 

 be allowed to ferment too long. Strict attention to these 

 details will commonly remove the trouble. 



The bacteria which produce sour bread do not, however, 

 come wholly from the use of impure yeasts, for the flour 

 itself is likely to contain some organisms which may cause 

 this trouble. A sour taste is much more likely to be 

 found in bread made from poor grades of flour than in 

 that made from the higher grades. This is perhaps due 

 to the fact that, owing to difference in the method of 

 manufacture, the lower grades of flour contain a larger 

 number of bacteria. The same trouble is also sometimes 

 caused by the use of unclean utensils in the mixing of the 

 dough, or by leaving the dough to rise in a dish not thor- 

 oughly washed. Unclean utensils are sure to have a large 

 number of bacteria attached to them, and these bacteria, 

 becoming mixed with the dough, grow there readily side 

 by side with the yeast. 



Slimy Bread. In recent years it has been noticed that, 

 a few hours after baking, bread sometimes becomes slimy. 



