PAET VIII 



Bacteeia and Fermentation 



CHAPTER XLIV 

 BACTERIA IN BREAD-MAKING 



In the making of ordinary bread, bacteria play a 

 subordinate part. The work of fermentation is accom- 

 pHshed by yeasts which change the sugar 'derived from 

 the starch into alcohol and carbon dioxid. On the other 

 hand, in the making of bread from sour dough, bacteria 

 are associated with the yeasts and produce the flavors 

 characteristic of such bread. Large quantities of sour- 

 dough bread are made in certain parts of Europe, where 

 rye flour is used almost exclusively in the baking of 

 bread. It has been found that the bacteria of the lactic- 

 acid group are prominently represented in sour dough. 

 Among the acids formed by them, acetic and lactic acid 

 are present in large proportion, particularly the latter, 

 which is not driven off in the process of baking and im- 

 parts a sour taste to the bread. 



Bread faults. — Apart from the r61e played by bacteria 

 in the making of bread, as just noted, microorganisms 

 bear, under certain conditions, a direct relation to what 

 may be termed its keeping quality. It has been observed 



(447) 



