480 



Mr. S. B. Schryver. Investigations on the [Mar. 6, 



caseinogen in sodium hydroxide equimolar with half- saturated lime water 

 was investigated. It was found that a precipitate was formed (apparently 

 by double decomposition) only when the concentration of the calcium salt 

 was within certain definite limits. The reactions form an " irregular series " 

 similar to many others where one of the reacting substances is a complex 

 colloid. If rennet is added to a mixture in which precipitation is inhibited 

 by excess of calcium salt an action takes place, and a precipitate is formed 

 shortly after the addition of the ferment. 



5. If the optimal amount of calcium salt is present, precipitate formation 

 can also be inhibited by the presence of milk serum, Witte's peptone, or 

 even glycine. The addition of rennet to such mixtures can cause precipita- 

 tion, provided that not too much inhibitory substance is present. The 

 amount of calcium salt also influences the reaction, which depends therefore 

 on the relative quantities of various products present in the system. The 

 relative influence of these substances has not yet been investigated in 

 detail. The precipitating power of calcium salts other than the chloride 

 has also been investigated. 



6. If solutions of calcium chloride or the salts of another alkaline earth are 

 added to a saturated solution of natural caseinogen in ^ sat. Ca(OH) 2 no 

 precipitate is formed at room temperature. If, however, the mixtures are 

 warmed slightly (to 25°), a typical clot is formed within certain limits of 

 concentration of the calcium chloride. This shrinks, and gives on treatment 

 with alcohol an indiarubber-like mass, and behaves, generally, in a manner 

 characteristic of the milk clot obtained by rennet. In optimal concentrations 

 of the calcium salt, clot formation can also be inhibited by the presence of 

 milk serum, Witte's peptone and glycine. The addition of rennet to mixtures 

 containing these inhibitory substances can cause the clot to form directly. 



7. There is reason to believe that the clot is formed from free caseinogen or 

 metacaseinogen and not from the calcium salt. The chief are : — 



(a) The clot after addition of calcium chloride forms only on warming, and 

 there is evidence that the calcium caseinogenate, under these conditions, 

 undergoes hydrolytic dissociation. 



(b) The clot can, however, form in the cold, if the caseinogenate solution is 

 previously treated with carbon dioxide. 



(c) The clot can be formed from sodium caseinogenate solutions, in the 

 absence of calcium, if the latter are treated first with carbon dioxide and 

 then with rennet. 



8. Calcium (but not sodium) caseinogenate solutions clot on addition of 

 rennet in the absence of calcium chloride. Clot formation under these 

 conditions is, however, inhibited by relatively low concentrations of milk serum. 



