CHURNING 279 



Size of Fat Globules. Cream in which the small fat globules 

 greatly predominate churns with difficulty while cream with 

 large average globules churns quickly. As previously stated the 

 formation of butter granules is dependent in part on the co- 

 alescence of the fat globules. In order for the fat globules to 

 coalesce, the fat must be partly or wholly solidified. For the 

 solidification of the fat it is necessary that the physical equilibri- 

 um of the fat globules be disturbed and partly destroyed. Other 

 things being the same, the chief factor keeping the fat globules 

 intact is the surface tension. The forces which overcome and 

 partly destroy the effect of the surface tension are greater in 

 their effect on the large globules than on the small globules, 

 the equilibrium of the large globules is more easily disturbed, 

 Therefore they solidify more readily and coalesce more quickly. 

 Again, the effect of the concussion in the churn, and the ease 

 of coalescence are intensified in the case of the large globules, 

 because they strike each other and the sides of the churn oftener 

 and with greater force than do the small globules. 



This is one of the reasons why milk from stripper cows in 

 which the fat globules are usually relatively small, often churns 

 with great difficulty. And since, in winter, the great majority of 

 the cows supplying the creamery are well advanced in their 

 period of lactation, it is in winter that the majority of the churn- 

 ing difficulties occur. The diameter of the fat globules in strip- 

 per milk averages about one-third of that of the fat globules of 

 milk from cows during the first two to three months of lactation. 



The size of the fat globules is also very materially affected 

 by breed, the fat globules in milk of the Channel Island cows 

 averaging much larger than those of the Holsteins and Ayrshires. 

 This explains in part, why cream churned on the farm and 

 produced exclusively from Holsteins and Ayrshires, at a time 

 when the cows approach the end of their period of lactation, 

 often churns with great difficulty. In the creamery the factor 

 of breed of cows is of much less importance. As the cream 

 supply territory of most creameries embraces a varied mixture 

 of the several breeds and grades of dairy cattle, the danger of 

 churning difficulties due to effect of breed on the size of the fat 

 globules, is a negative quantity. 



