t 644 ] 



1,112. The composition of milk differs very much accord- 

 ing to the food and the yield. The larger the quantity 

 given by a particular cow the poorer it is in fat. Watery 

 food also results in poor milk. The last strippings are 

 the richest in fat. The average composition of milk out of 

 a herd of 20 cattle is fairly uniform. 



1.113. Milk is not a homogeneous substance. The butter 

 fat which has the specific gravity of '91 being suspended in 

 a solution of sugar (lactose) and proteids the specific gravity 

 of which is 1*03, is not evenly distributed through the whole 

 quantity of milk. One sample of milk from the same cow 

 therefore differs from another sample, and a representative 

 sample from a particular cow is difficult to get, though the 

 mixed milk of a large dairy is fairly even in composition. 



1.114. Buffalo butter, having a higher melting point than 

 cow's butter can be easily distinguished from the latter. 

 Ghee contains less water and casein than butter and it has a 

 slightly higher melting point and specific gravity. Butter 

 fat consists chiefly of glycerides of palmitic and oleic acids. 

 The glycerides of stearic, myristic, lauric, capric, capryllic, 

 caproic and butyric acids, are also present in small quantities. 

 The glycerides of oleic, capric, capryllic, caproic and butyric 

 acids are fluid in ordinary temperature, the remaining gly- 

 cerides being solid. In summer the proportion of fluid fats is 

 greater than in winter. Food also has a great effect on the 

 fats of butter. Rape-cake, cotton cake, oats, and wheat-bran 

 produce harder butter, while lih seed cake, peas, and barley 

 produce soft butter. 



1,115. When butter or ghee becomes rancid, the glycerine 

 compounds are decomposed and the acids set free. The 

 butyric, caproic, capryllic and capric acids having a strong 

 smell, produce the characteristic smell of rancid butter and 

 ghee. Since these acids are also slightly soluble in water 

 and more so in milk, the disagreeable smell of rancid butter 

 pan -be got rid of by several washings with water, or better 



