CHURNING 273 



The reason for this is obvious. As previously explained, the 

 increase in the size of the butter granules during- the early 

 stages of the churning process is slow, due to the small initial size 

 of the fat globules and to the obstructing foam. Numerous pro- 

 gressive steps of adhesion between fat globules and later be- 

 tween butter granules are necessary before the breaking point 

 is reached. This requires time, and yet, during all this time 

 there is no visible sign of butter formation. 



Just before the breaking point the contents of the churn 

 are still cream. But the butter granules, though still invisible 

 to the naked eye, have reached the maximum size at which 

 their reduced surfaces are still capable of sustaining their 

 emulsion with the skim milk in the form of cream. One more 

 union between each two of these relatively large butter granules, 

 causing the granules to be twice of this already relatively large 

 size, may break the emulsion, the resulting granules being too 

 large and their surfaces too small to still sustain their emulsion 

 in the skim milk of the cream. The result is that the skim 

 milk immediately breaks away from the butter granules and the 

 butter "breaks," and we have masses of butter granules on the 

 one hand and buttermilk on the other. 



The suddenness of the "breaking of the butter is further 

 intensified by the fact, that the relatively large size of the still 

 emulsified butter granules in the cream just before the breaking 

 point, facilitates the coalescence, or adhesion, of these granules 

 in the cream. The larger the granules before the breaking point, 

 the more easily they find each other, the more readily they col- 

 lide, and the accelerated force of impact between these larger 

 granules increases their power of adhesion. When they collide 

 they stick together. Simultaneous with the break of the tension 

 of the fat-in-skim milk emulsion, much of the incorporated air 

 also is liberated, further quickening the breaking of the emulsion. 

 Hence, when this critical point is reached, one or a few more 

 revolutions of the churn suddenly transforms the emulsion of 

 cream into solid butter and fluid buttermilk. The butter "breaks" 

 abruptly. 



The foregoing discussion makes it clear that the churning 

 process resolves itself into a change from a fat-in-skim milk 



