280 CHURNING 



Chemical Properties of the Butterfat. The chemical make- 

 up of the butterfat influences its churnability largely through its 

 effect on the melting point and mechanical firmness of the fat. 

 While the desired degree of solidification of the fat globules is 

 chiefly a matter of temperature adjustment of the cream before 

 churning, it is very materially influenced by the chemical com- 

 position of the fat. Butterfat is a mixture of fats with different 

 melting points, different solidifying points and of varying me- 

 chanical firmness. 



Experimental results by the author 1 and others show that, 

 while there appears to be no definite relation between the per 

 cent of volatile acids, as arbitrarily expressed by the Reichert- 

 Meissl number, and the per cent of oleic acid, as expressed by 

 the Iodine number, and the melting point, and while the relative 

 proportion of soluble acids exclusive of butyric and that of in- 

 soluble acids exclusive of oleic acid is evidently an important 

 factor related to the melting point, it appears reasonable to con- 

 clude, that the volatile acids and the oleic acid do influence the 

 melting point to a very marked degree and that there is a strong 

 tendency for the melting point to follow, inversely, changes in 

 the per cent oleic acid and volatile fatty acids. 



Since the volatile fatty acids have a much lower melting 

 point than the oleic acid, it is obvious that variations in the 

 amount of the former, present in the butterfat, exert the greater 

 influence on the melting-point of the fat. However, the volatile 

 fatty acids are present in relatively small amounts and their 

 changes, expressed in percentage of the total fat, are usually 

 slight. Oleic acid, on the other hand, constitutes a large por- 

 tion of the total butterfat and it often varies between wide limits 

 (35 to 50%). Hence the fluctuations in the amount of oleic acid 

 present are looked upon as, and have been found to be, respons- 

 ible for, in a large measure, variations in the melting point. 



Butterfat in which the fats with high melting points and 

 great firmness are present in excess and at the expense of the 

 fats with low melting points and soft texture, churns relatively 

 slowly. The fat globules solidify at a relatively high tempera- 

 ture, and unless the churning temperature has been correspond- 

 ingly raised, they are prone to become excessively firm, their 



1 Hunziker, Spitzer and Mills, Purdue Bulletin No. 159, 1912. 



