THE COMPOSITION OF MILK 3 



ing the per cent of solids from 100, as the loss in 

 weight during evaporation is the water expelled 

 as steam. There are rarely more than 88 pounds of 

 water in 100 pounds of milk ; average milk contains 

 about 87 per cent, while some of the richest milks 

 contain 86 per cent or less. The milk solids, unless 

 obtained in a specially constructed water oven, are 

 brown in color, due to slight charring of the sugar 

 and other compounds. The solids of milk are some- 

 times termed dry matter and sometimes solid matter. 

 They are composed of fat, casein, sugar, albumin, ash, 

 and other compounds found in smaller amounts. 



4. Milk Fats. Average milk contains about 3.5 

 per cent of fat ; some normal samples may contain 

 3 per cent or less, while others may contain 5 per 

 cent or more. Fat is the most variable constitu- 

 ent in milk. Cream contains ordinarily from 18 to 

 35 per cent of fat, and well-made butter about 85 per 

 cent. For butter-making purposes the value of the 

 milk is directly proportional to its fat content. Milk 

 fat is mainly familiar as the product obtained by 

 churning cream. Milk fat and commercial butter, 

 however, are not synonymous terms. By milk fat 

 is meant the pure dry fat, free from water, salt, or 

 casein, while butter contains all of these materials 

 in variable amounts. The determination of the fat 

 in milk by the Babcock test is discussed in the 

 second chapter of this work, and the composition 

 and properties of the fats are considered in other 

 chapters. 



