BACTERIA IN BUTTER-MAKING. 



229 



odor, almost like that of putrefaction. Some produce a tal- 

 loicv butter, others terras-tasting, &r putrid butter. In general 

 it is the lactic bacteria which produce the desired results, while 

 other types, if excessively abundant, give rise to the abnormal 

 flavors (Fig. 29). 



Careful study with the common species of dairy bacteria has 

 shown that the majority of the species appear to have no es- 

 pecial influence and may grow in the cream without any 

 marked effect upon the butter. Some of them, however, pro- 



FIG. 29. 



Several varieties of bacteria from ripening cream : a and b produce unpleasant-tasting butter, c 

 and d produce good butter, e has no effect on butter. 



duce changes in the cream which give rise to the products 

 imparting the desired flavor and aroma. Others produce 

 changes which give rise to an abnormal ripening, resulting in 

 an improper consistency in the cream, and more especially in 

 unpleasant flavors and aromas. These, of course, the butter- 

 maker desires to keep out of his cream, for it is these, in large 

 degree at least, which produce the inferior qualities of butter 

 coming from improperly ripened cream. According to our 

 present knowledge, the majority of the species of dairy bac- 

 teria may be looked upon as neutral, so far as concerns their 



