8 BUTTER-MAKING 



When pure butter-fat is rapidly cooled, it solidifies into one 

 solid mass; but if allowed to cool gradually, part of it solidifies, 

 and part of it remains a liquid longer than other parts. This 

 seems to indicate that some fats with a high melting-point 

 separate out from the fats with a low melting-point. This 

 behavior of pure butter-fat is not well understood, as it con- 

 tradicts the now accepted theory that the different fats are 

 in chemical combination with each other, rather than a me- 

 chanical mixture of different glycerides of fat. 



Glycerides of Fat. By this term we understand that the 

 fatty acid radicals are in chemical combination with the glycerol 

 (glycerine) radical, thus: 



Fatty acid radicals. 

 Glycerol radical, f C 4 H 7 2 (Butyric) 



C 3 H 5 j C 18 H 33 2 (Oleic) 



The chemical formula for glycerine is: 



Hydroxyl groups. 

 Glycerol radical. ! OH 



C 3 H 5 j OH 



I OH 



Comparing these two formulas, their difference and simi- 

 larity are easily observed, and the reason why the term "Gly- 

 ceride of Fat " has been applied to such a compound is evident. 



Condition of Fat. Whether the fats in milk exist in chem- 

 ical combination, or whether they exist as glyceride of butyrin, 

 stearin, olein, etc., in the form of a mechanical mixture, is a 

 question in dispute. If they exist in the latter form, the com- 

 position of the different fats must be thus: 



Butyrin. Olein. Stearin. 



fPTTO ( P TT r f P TT /~\ 



I ^ 4 n 7 V-/2 | v./i 8 n 33 l^2 f ^18- n -35v-'2 



C 3 H 5 j C 4 H 7 2 C 3 H 5 j Ci 8 H 33 2 C 3 H5 ] Ci 8 H 35 2 etc., 

 I C 4 H 7 2 | Ci 8 H 33 O2 ! Ci 8 H 3 sO2 



