10 THE BOOK OF CHEESE 



the formation of this coagulum (curd) , the fat is imprisoned 

 and held. The casein compounds in the curd hold the 

 moisture and give firmness and solidity of body to the 

 cheese. Casein contains the protein materials in which 

 important ripening changes take place. These changes 

 render the casein more soluble, and are thought to be 

 the source of certain characteristic cheese flavors. 



13. Milk-sugar. Milk-sugar (lactose) is present in 

 solution in the watery part of the milk. It forms on the 

 average about 5 per cent of cow's milk. Since it is in 

 solution, cheese retains the aliquot part of the totaj 

 represented by the water-content of the cheese, plus any 

 part of the sugar which has entered into combination with 

 the milk solids during the souring process. The larger 

 part of the lactose passes off with the whey. Lactose 1 

 is attacked by the lactic-acid bacteria and by them is 

 changed to lactic acid. Cheeses in which this souring 

 process goes on quickly, soon contain a large enough 

 percentage of acid to check the rotting of the cheese by 

 decay organisms. Without this souring, most varieties 

 of cheese will begin to spoil quickly. For each variety 

 there is a proper balance between the souring, which 

 interrupts the growth of many kinds of putrefactive 

 bacteria, and the development of the forms which are 

 essential to proper ripening. 



14. Albumin. This is a form of protein which is in 

 solution in the milk. Albumin forms about 0.7 per 

 cent of cow's milk. It is not coagulated by rennet. Most 

 rennet cheeses, therefore, retain only that portion of the 

 total albumin held in solution in the water retained, as 

 in the case of milk-sugar. Albumin is coagulated by heat, 

 forming a film or membrane upon the surface. There 



1 Wis. Exp. Sta. Kept. 1901, pages 162-166. 



