54 MILK ANALYSIS 



Butter-fat is distinguished from other animal fats in that it 

 contains a notable proportion of acid radicles with a small 

 number of carbon atoms. Thus, about 91 per cent, consists 

 of palmitin and olein and the remainder of butyrin and ca- 

 proin, along with small amounts of caprylin, caprin, myristin, 

 and some others. According to the experiments of Hehner 

 & Mitchell, stearin is present only in very small quantity. 

 The exact arrangement of the constituents is unknown. 



The composition of commercial butter usually varies within 

 the following limits: 



Fat, 78 per cent, to 94 per cent. 



Curd, .1 " "3 



Water, 5 " "14 



Salt, o " " 7 " 



Butter containing over 40 per cent, of water is sometimes 

 sold. Such samples are pale and spongy, lose weight, and 

 become rancid rapidly. 



The official methods of the A. O. A. C. for the analysis of 

 butter are as follows: 



Preparation of the Sample. If large quantities of butter 

 are to be sampled, a butter trier or sampler may be used. 

 The portions thus drawn, about 500 grams, are to be per- 

 fectly melted in a closed vessel at as low a temperature as 

 possible, and when melted the whole is to be shaken violently 

 for some minutes until the mass is homogeneous and suffi- 

 ciently solidified to prevent the separation of the water and fat. 

 A portion is then poured into the vessel from which it is to be 

 weighed for analysis, and should nearly or quite fill it. This 

 sample should be kept in a cold place until analyzed. 



Water. From 1.5 to 2.5 grams are dried to constant weight 

 at the temperature of boiling water, in a dish with flat bottom, 

 having a surface of at least 20 sq. cm. The use of clean dry 

 sand or asbestos with the butter is admissible, and is necessary 

 if a dish with round bottom be employed. 



