CASEINOGEN 11 



When caseinogen is acted upon by formaldehyde, the amino 

 groups condense with the H-CHO to form methylene deriva- 

 tives. The resultant compounds are not digested by trypsin 

 but can be decomposed by steam and the formaldehyde quan- 

 titatively recovered in the distillate. On the formation of 

 methylene derivatives, the alkalinity due to amino groups dis- 

 appears, and the caseinogen salt, which before condensation 

 reacted neutral to phenolphthalein, becomes acid and can be 

 quantitatively titrated with alkalies. This reaction is the 

 basis of the aldehyde value (vide p. 75). 



Caseinogen, on hydrolysis by pepsin, trypsin, or dilute 

 acids, undergoes proteoclastic digestion with the formation of 

 caseinogen proteoses or caseoses, as they have been called, which 

 are soluble in water. These caseoses have been subdivided 

 into proto and deutero caseoses by their solubility in ammo- 

 nium sulphate solutions of certain concentration. 



The ultimate products of the hydrolysis of caseinogen have 

 been extensively investigated and the results of various ob- 

 servers, obtained with caseinogen from various sources, are 

 given in Table II. 



Caseinogen exists in milk as a salt combined with phos- 

 phate of calcium, and although the composition of this com- 

 plex has been investigated by many chemists during the last 

 sixty years, it is impossible even yet to state that it is defi- 

 nitely established. Richmond, from an analysis of the mate- 

 rial separated by filtration through a porous cell, assumes that 

 caseinogen exists in milk as a double calcium sodium caseino- 

 genate combined with half a molecule of tricalcic phosphate. 

 Ci62H255N4iSPO52-Ca-Nai(Ca3P20 8 ). The quantity of acid 

 required for the displacement of the sodium atom in this formula 

 by hydrogen, would be 8.3 c.cms. of normal acid per litre of 

 milk, and Richmond found that on adding 8.6 c.cms. N. hydro- 

 chloric acid or sulphuric acid, the caseinogen was precipitated 

 on boiling, and that the acidity of the serum was equal to that 

 of the milk after boiling. L. L. Van Slyke and Bosworth 10 

 have pointed out that deductions based on the acidity of milk 



