BACTERIA IX BUTTER-MAKING. 22/ 



produced by the ripening of cream comes from bacterial action 

 and not from the action of unorganized ferments. 



This extraordinary growth of bacteria cannot occur without 

 producing great changes in the nature of the cream. The 

 changes are in general similar to those already mentioned as 

 occurring in milk. The cream sours, thickens, and acquires 

 a pleasantly sour taste and characteristic odor. Butter made 

 from such cream is delicately flavored and of high quality. 



There is no difficulty in understanding how the growth of 

 bacteria in the cream accomplishes the purposes aimed at in 

 the ripening. Churning consists simply in shaking the cream 

 until the globules of fat are brought into contact with each 

 other. As soon as they come in contact they fuse together 

 and, as the agitation continues, the masses of adhering globules 

 become larger until they are finally large enough to be re- 

 moved from the liquids as grains of butter. Anything which 

 prevents the fat globules from coming in contact with each 

 other delays the churning and decreases the yield. Now in 

 fresh cream the fat globules do not float around freely in the 

 liquid but appear to be held by some albuminous substance. 

 Apparently they are partly entangled in a very minute, fibrous 

 mass, somewhat similar to the fibrin of the blood, and this has 

 a restraining effect upon the adhesion of the globules. This 

 fibrin is softened by the action of the bacteria so that, after 

 ripening, the fat particles are more free to unite, the churning 

 is made easier and the yield of butter larger. When cream is 

 separated by the separator instead of by gravity this fibrin 

 material is removed from the cream by the force of the cen- 

 trifugal motion. Hence separator cream does not need ripen- 

 ing for the purpose of making the churning easier, and it 

 churns readily enough even when fresh. 



But separator cream does need ripening for the purpose of 

 developing the flavor, which is the most important result of 

 ripening. Sweet cream butter has very little taste and the 



