380 FUNDAMENTALS OF AGRICULTURE. 



two or three days. The curd thus obtained is strained 

 from the whey and, after being salted, makes sour-milk 

 or cottage cheese. This kind of cheese does not have 

 to undergo any ripening process, but is consumed within 

 a few days after it is made. 



Composition of Cheese. Cured Cheddar cheese is 

 composed of about 32 per cent, of water, 34 per cent, 

 of butter fat, 28 per cent, of casein and albumen, 3 per 

 cent, of organic acids (mainly lactic acid, the acid of 

 sour milk), and 3 per cent, of salt. "Full-cream 

 cheese " means cheese made from milk containing all 

 the cream it ordinarily had. Milk is sometimes partly 

 skimmed before being coagulated with rennet, and the 

 product thus obtained is called part-skim, half-skim 

 cheese, etc. Full-skim cheese is also manufactured at 

 times from pure skim milk, but this does not make a 

 palatable food, being hard, horny and flavorless, even 

 when cured for months. In many states the manu- 

 facture of part or full-skim milk cheese is prohibited 

 by law. 



Other Dairy Products. Condensed Milk is manu- 

 factured from whole milk or partly skimmed milk by 

 evaporating a certain portion of the water contained 

 therein. The volume of the milk is reduced to one- 

 third or more in the process of evaporation, which 

 takes place in large vacuum pans. Condensed milk 

 should contain at least 8 per cent, of butter fat, and be 

 free from any foreign substance, except cane sugar, 

 which is added in the manufacture of sweetened con- 

 densed milk. Condensed milk makes a good substi- 

 tute for whole milk or cream, and is used in cases where 

 whole milk cannot be obtained, e. g., on long voyages, 

 in mining camps, etc. 



Milk Sugar is obtained by evaporating the whey and 

 allowing the crystals of milk sugar to form. It is used 

 extensively in the manufacture of infant foods and me- 

 dicinal preparations. 



Buttermilk and Whey are, as we have seen, by-prod- 

 ucts in the manufacture of butter and cheese. Both of 



