406 Bacteria in Relation to Country Life 



We see, therefore, that the ripening of cream is 

 equivalent to the accumulation in it of certain products. 

 Under properly controlled conditions, the quantity and 

 quality of these products are satisfactory to the butter- 

 maker, for they impart to his butter the desired proper- 

 ties. Experience has taught him, at the same time, 

 that it is not safe to depend on the spontaneous bacterial 

 changes in the ripening cream for the production of 

 high-grade butter. The method is not only slow, but 

 uncertain. Occasionally the lactic-acid bacteria do not 

 gain the ascendancy in the ripening cream. Other 

 species become prominent and produce substances that 

 impart to the butter objectionable flavors, or injuriously 

 affect its keeping quality. The butter-maker must 

 attempt, therefore, to control the ripening process by 

 adding to the cream large quantities of desirable bac- 

 teria, such additions being known as "starters." 



Starters. — If a quantity of cream sours normally 

 and produces butter of superior quality, it must contain 

 bacteria capable of bringing about this result. A starter 

 is a quantity of inoculating material and is valuable 

 only when it contains the proper kinds of bacteria, 

 that is, bacteria capable, not merely of producing cer- 

 tain chemical changes, but, also, of growing with suf- 

 ficient rapidity to overcome the other organisms present 

 in the cream. 



A pure culture of some germ capable of carrying 

 forward the ripening process in a satisfactory manner 

 may be added to the cream. This is actually done on a 

 more or less extensive scale in the dairy districts of 

 northern Europe, notably in Denmark. A limited use 



