FUNCTIONS OF MILK CONSTITUENTS I79 



second function is to retain whey in the curd in 

 desired amounts, while, at the same time, permit- 

 ting superfluous whey to escape from the mass of 

 curd. The power of casein to hold moisture is 

 somewhat like that of a sponge. Special experi- 

 ments at the New York experiment station have 

 shown that one pound of dry casein can easily 

 absorb and hold about one pound and a quarter of 

 water. Fat has, of course, comparatively little 

 water-holding power, so that this function falls 

 almost entirely on casein. It is obvious that this 

 special work can be done by no other constituent 

 of milk, and thus casein is recognized as the water- 

 holder in cheese. 



In the finished product, casein, or rather, the 

 compound formed from it, performs two important 

 and peculiar functions, (i) It gives to the cheese 

 firmness and solidity of body under a wide range 

 of temperature, conditions which are requisite for 

 its keeping and convenient handling. The casein- 

 derived product in reality constitutes the firm 

 framework or skeleton which gives permanence to 

 the form of the cheese. (2) It furnishes the protein 

 material in which, it is believed, take place those 

 changes that result in characteristic cheese flavors, 

 while, at the same time, it is converted into soluble, 

 nutritive compounds, which add largely to the value 

 of the cheese as food. The peculiar properties of 

 casein when made into cheese are such that its 

 presence in excess in relation to fat or moisture 

 causes serious deterioration in some of the proper- 

 ties of the cheese. For instance, when an excess of 

 casein is used, as in the case of skim-milk cheese, 



