THE ANALYSIS OF BUTTER 67 



The Examination of the Fat. Butter fat is of 

 peculiar composition, consisting of complex glycerides 

 containing lower fatty acids, chiefly caproic and butyric 

 acids ; these are characterised by being soluble in 

 water, and volatile with steam, while the fatty acids of 

 almost all other fats are insoluble and non- volatile ; 

 furthermore the presence of the lower fatty acids in 

 the glycerides causes them to have a softer consistency 

 than if only the insoluble acids were present, and a 

 comparatively small amount of the acids of the oleic 

 and more unsaturated series is present. To obtain a 

 fat of the consistency of butter without the lower fatty 

 acids, a larger amount of acids of the oleic, &c., series 

 must be present. The presence of the lower fatty acids 

 gives a high specific gravity to the glycerides, and 

 causes them to crystallise badly. 



In addition to these facts on which the broad prin- 

 ciples of butter analysis are based, certain vegetable 

 oils, especially sesame oil, give characteristic reactions, 

 and it has been recommended that by international 

 agreement all margarine shall legally be made to con- 

 tain 10 per cent, of sesame oil. 



The addition of margarine to butter may be detected 

 by- 



(a) A lowered proportion of volatile acids ; 



(b) A lowered proportion of soluble and increased 



proportion ot insoluble acids ; 



(c) An increased mean molecular weight ; 



(d) A decreased density ; 



(e) A more marked crystallisation ; 



properties all chiefly depending on the lowering of the 

 amount of caproic and butyric acids in the glycerides, 

 and 



( / ) An increased iodine absorption ; 



(g) An increased refractive index ; 

 properties chiefly depending on the increase of the 

 unsaturated acids in the glycerides ; to those may be 

 added 



(h) A turbidity of the fat on melting at a low 



