274 CHURNING 



emulsion, such as exists in milk and cream, into a buttermilk-in- 

 fat emulsion, such as exists in butter. This transformation of 

 emulsions, or of cream into butter, is brought about funda- 

 mentally by solidification of the fat globules and by subsequent 

 coalescence of the solidified fat globules, forming butter granules, 

 and by progresive adhesion or uniting of the butter granules. 



Solidification. The solidification of the fat globules is caused 

 by low temperature and concussion. 



The solidifying point of butterfat, like the melting point, is 

 not constant. It varies particularly with the chemical compost 

 tion of the butterfat. Thus the fats of the harder glycerides, such 

 as the myristin, stearin and palmitin, have a higher solidifying 

 point than the fats of the softer glycerides, such as the fats 

 of the volatile fatty acids and the olein. Hence the solidifying 

 point fluctuates according to the relative proportion of these 

 several fats in the mixed fat. 



At the temperature of the animal body, 98 to 100 F., but- 

 terfat is liquid. At ordinary temperatures (room temperature) 

 butterfat contains both solid and liquid elements. By lowering 

 the temperature, fractional crystallization of the butterfat is ef- 

 fected, the harder glycerides crystallizing first. As the tem- 

 perature drops, more of the softer glycerides begin to crystallize. 

 The extreme range of the solidifying point of the mixed butter- 

 fat lies between about 15.5 degrees C. to 30 degrees C. (60 to 

 80 degrees F.) Under normal conditions the range of tem- 

 perature is confined to much narrower limits, not falling below 

 about 18 degrees C. nor exceeding 24 degrees C. (65 to 75 degrees 

 F.) and averaging about 21 degrees C. (70 degrees F.). 



In order for the fat globules to form butter granules, it is 

 necessary therefore, to lower the temperature of the cream suf- 

 ficiently to insure solidification of the fat in the fat globules. 

 The reason why the churning temperature of the cream must be 

 dropped below the minimum temperature at which the mixed 

 fat solidifies, must be attributed in part at least to the fact, that 

 mere solidification, while it causes the cream to churn, does not 

 necessarily give the butter granules the desired firmness. Lower 

 temperatures are needed to render the butter granules sufficiently 



