10 A Neiv Dairy Industry. 



spect to the curdling of the casein, the content of 

 salts, the absolute content of nutrients and the rela- 

 tion of the various constituents. The nature of the 

 coagulated casein in the stomach depends upon the 

 casein solution, the content of soluble calcium salts 

 and the acidity of the solution. Cow's milk is in 

 these three respects unfavorable to the best coagula- 

 tion, for it contains twice as much casein, six times as^ 

 much lime and is three times as acid as human milk,, 

 while this latter contains but one-third as much of" 

 acid phosphates as cow's milk. 



Casein forms three chemical compounds with cal- 

 cium or sodium dependent on the predominant re- 

 action the mono, di and tri-calcic (or sodic) casein. 

 Only the dicalcic or disodic casein compounds are 

 curdled by rennet in the presence of water soluble 

 lime salts, and the completeness of the curdling de- 

 pends on the amount of lime salts ; we may, there- 

 fore, attribute the compactness of the casein curdling- 

 in cow's milk to an increased alkalinity. The studies 

 of Bechamp show that casein is not a soluble sub- 

 stance which may be coagulated by acids, but that it 

 is an insoluble substance forming soluble compounds, 

 caseinates, with alkalies and lime, and that the in- 

 soluble casein may be precipitated from these com- 

 pounds by acids which combine with the bases of 

 caseinates. The change in the casein by the action 

 of rennet has no connection with the reaction. We 

 shall see later what effect heating produces on the di- 

 gestability of casein and on the milk proteids in general.. 



