276 CHURNING 



Coalescence. Coalescence is the second necessary factor for 

 the formation of butter granules By coalescence is meant the 

 uniting and adhering together of the fat globules and butter 

 granules. The power of the fat globules to coalesce is largely 

 determined by the extent of solidification and the amount of con- 

 cussion. It is also affected by the size of the fat globules, by 

 adsorption and by the viscosity of the cream. 



In liquid form the fat globules cannot coalesce to the extent 

 of forming butter granules. In warm cream set at rest they may 

 run together, "oiling off" and forming a continuous layer of oil. 

 In cream at any temperature not low enough to cause solidifica- 

 tion or partial solidification of the fat, when subjected to agita- 

 tion such as is produced in the revolving churn, the fat globules, 

 instead of coalescing tend to diminish in size, due to the effect 

 of their surface tension, adsorption and the viscosity of the 

 cream. For this reason cream does not churn out, and but- 

 ter granules do not form when the temperature is too high to 

 effect at least partial solidification. 



On the other hand, coalescence and the formation of butter 

 granules is greatly delayed, if not made impossible, when the 

 degree of solidification has been carried so far, as to cause the 

 fat globules and the small butter granules to be very hard. In 

 this case the adhesive property, or stickiness, of the fat globules 

 and of the initial butter granules is greatly reduced, the impres- 

 sion which they suffer when they collide is very slight, the surface 

 of contact is therefore too small and the individual globules and 

 granules are too firm to readily adhere to each other when 

 they collide. For this reason, cream that is churned at an ex- 

 tremely low temperature, or that has been held at a very low 

 temperature for a long time before churning, or the fat of which 

 has a relatively high melting point, churns with great difficulty. 



In order to give the fat globules an opportunity to coalesce 

 they must be subjected to concussion. This is obviously 

 produced by the operation of the churn. The more vigorous the 

 concussion, other things being equal, the greater their power 

 to coalesce and the more rapidly is the churning completed. 



Other conditions being the same, the time required for the 

 butter granules to form is determined by the size of the fat 



