170 AGRICULTURE. 



most of the albumen remains with the skim-milk 

 and buttermilk. In cheese-making albumen re- 

 mains in the whey, and is not incorporated into 

 the cheese. The very disagreeable odors char- 

 acteristic of decomposing milk are largely pro- 

 duced from albumen. 



j. Milk Sugar. This sugar, known by the 

 chemist as lactose, has the same composition as 

 common cane sugar (C, 2 H 22 O II H 2 O), and is 

 found only in milk. It appears, when separated, 

 as a fine white powder, with a mild, sweet taste. 

 Milk sugar is a common commercial article, be- 

 ing usually secured from whey as a by-product 

 of cheese-making. When milk is used for butter- 

 making almost all the sugar remains with the 

 skim-milk and buttermilk, while in cheese-mak- 

 ing it remains in the whey. Its chief impor- 

 tance in butter or cheese making is its relation 

 to the souring of milk or milk products, which 

 is due to the decomposition of the sugar through 

 the action of minute forms of plant life called 

 bacteria. By this act of decomposition, lactic 

 acid is produced from the sugar, and this gives 

 the common sour taste and causes the precipita- 

 tion of the casein, as seen in soured milk. 



4. Ash. This is the portion that would re- 

 main if milk were burned. It consists of a mix- 

 ture of several elements, the most important 

 being lime, iron, potash, magnesium, sulphur, 

 and phosphorus. These mineral matters are all 



