138 



Scientific Proceedings (119). 



calcium phosphates takes place during the holding process of 

 pasteurization. The fact that pasteurization of milk retards the 

 coagulability of the casein by rennet and the fact that this prop- 

 erty can be restored by the addition of calcium chloride to the 

 milk have been presented in support of the view that heat changes 

 some of the soluble calcium salts to an insoluble form. The experi- 

 mental evidence for such a change is, however, contradictory. 

 Solomin 1 noted that a little phosphorus falls out of milk when 

 the temperature is raised to 8o° C. Diffloth 2 found a decrease 

 of 26 per cent, in the soluble phosphates when milk was held at 

 6o° C. for 30 minutes. Rupp, 3 however, approached the problem 

 by filtering raw and pasteurized milk through a clay filter and 

 analyzing the filtrate for calcium and phosphorus. He found no 

 change in the calcium and phosphorus after holding the milk for 

 30 minutes at 68.3 0 C. Milroy 4 held the fresh milk at a tempera- 

 ture just below the boiling point for one hour and, after filtering 

 through an ordinary filter, noted a decline in calcium. He ex- 

 plained this result on the basis of a transformation of dicalcium 

 phosphate into basic calcium phosphate. Grosser made similar 

 studies on samples of milk which had been boiled for 5, 10 and 

 15 minutes, respectively, and noted a negligible loss in phosphor- 

 us in the filtrate, but a slight loss in calcium. 



Daniels and Loughlin 5 have recently obtained qualitative evi- 

 dence that calcium phosphates are thrown down when milk is 

 pasteurized by the holding process, in that they have noted a 

 nutritional calcium and phosphorus deficiency of such milk which 

 could be prevented by feeding the washings from the walls of the 

 vessel in which the milk was pasteurized or by addition of calcium 

 phosphate to the rations of the animals (rats) in the experiments. 



The explanation commonly held for the effect of heat on the 

 calcium phosphates of milk originated with Soldner who believed 

 that the calcium of milk is present as mono- and dicalcium phos- 



1 Solomin, P., Arch. f.Hyg., 1897, xxviii, 43. 



2 Diffloth, Paul, Bull. d. Sci. Pharm., 1904, x, 273; Zeit. Nahr. Genussm., 

 1906, xi, 455. 



• Rupp, Philip, U. S. Dept. of Agr., Bureau of Animal Ind. Bull., 1913, clxvi, 

 1-16. 



* Milroy, T. H., Biochem. Jr., 191 5, ix, 221. 



8 Daniels, A. L. and Loughlin, R. J., Biol. Chem., 1920, xliv, 381. 



