4 MODERN METHODS OF TESTING MILK 



from less than i to nearly 3 per cent, of each of tl 

 glycerides of other acids. Milk-fat contains aboi 

 12.5 per cznt. of glycerin in combination with tl 

 acids. The proportions of these constituents of mill 

 fat vary somewhat, and this variation influences tr 

 character of the milk-fat. Thus, palmitin and myri: 

 tin tend to make milk-fat harder, while olein and but 1 

 rin have the opposite tendency. 



The acids contained in milk-fat or butter-fat ma 

 be divided into two groups: (i) The acids in or 

 group (palmitic, oleic, myristic, stearic, lauric) ai 

 insoluble in water and non-volatile, while (2) tl: 

 other acids (butyric, caproic, etc.,) are more or le< 

 completely soluble in water and are volatile. Thes 

 differences afford a practical basis for distinguishin 

 pure butter from artificial butter. Of the fat-acic 

 contained in butter- fat, about 87.5 per cent, consisl 

 of the insoluble fat-acids, while in other forms c 

 animal fat (beef- fat, lard, etc.,) the amount of thes 

 insoluble fat-acids is considerably greater. The amour 

 of volatile fat-acids in milk-fat or butter-fat is muc 

 greater than in other forms of animal fat. 



Fat-globules in milk. Milk-fat is present in mill 

 not in solution, but suspended in the form of ver 

 small, transparent globules. Globules varying in siz 

 between one twenty-five hundredth and one fifteer 

 thousandth of an inch in diameter are the ones mo< 

 commonly present. The average size of fat-globule 

 in milk is somewhat more than one ten-thousandth c 

 an inch in diameter. The smaller globules are mor 

 numerous than the larger ones. In one drop of aver 

 age milk there are more than one hundred million fat 



