1018 EXPERIMENT STATION RECORD. 



the results showing that the material contained large quantities of proteids, lecithin, 

 and cholesterin. It was thought that the material was brain or nervous tissue pre- 

 served with formalin. Objections to its use are presented. 



Some of the relations of casein and paracasein to bases and acids, and 

 their application to Cheddar cheese, L. L. Van Slyke and E. B. Hart (New 

 York stale Shi. Bui. .''</, pp. 37). — In these investigations, which are a continuation 

 and extension of the work reported in Bulletin 214 of the station ( E. S. R., 14, p. 607), 

 the authors have studied the relation between milk casein and the salt-soluble com- 

 pound previously called a casein mono-salt; the relation between the 2 series of 

 compounds previously called casein mono-salts and casein di-salts; and the relation 

 of casein and its derivatives to paracasein and its derivatives. The following com- 

 pounds have been prepared and studied: Base-free casein, basic calcium casein, neu- 

 tral calcium casein, casein salts of acids, base-free paracasein, basic calcium paracasein, 

 neutral calcium paracasein, and paracasein salts of acids. 



With the omission of headings the results as summarized by the authors follow: 



"Preparations of casein free from ash or nearly so were made by precipitating dilute 

 skim milk with acids, removing the acid and inorganic matter by repeated filtra- 

 tion and trituration with water in a mortar. The process required several days. 



"Preparations were made with base-free casein, in which the proteid combined with 

 about 2.41) per cent of calcium oxid. One such preparation was made by triturating 

 together calcium carbonate and the base-free casein suspended in water, and another 

 by dissolving base-free casein in limewater and making this neutral to phenol- 

 phthalein by acid. 



"Bytreating base-free casein dissolved in limewater with acid until the reaction is 

 almost neutral to litmus, there is formed a compound of casein and calcium oxid 

 containing about 1.50 per cent of calcium oxid. 



"Rennet enzyro coagulates neither neutral nor basic calcium casein. Neutral cal- 

 cium casein after treatment with rennet is coagulated at ordinary temperatures by 

 soluble calcium salts. Soluble calcium salts, as calcium chlorid, coagulate both 

 neutral and basic calcium casein on warming to ;■'„"> to 45° (J. 



"In its behavior toward soluble lime salts on warming and at ordinary tempera- 

 tures after treatment with rennet, neutral calcium casein behaves like milk casein, 

 and casein is probably present in cows' milk as the neutral calcium casein. 



"A base-free casein, prepared either directly from milk or by treating a limewater 

 solution of free casein with an acid to the point of acidity with Litmus, is readily soluble 

 in warm 5 percent salt solution &nd in hot 50 per cent alcohol. This body, when 

 freshly prepared and sufficiently warmed is very plastic and ductile. It behaves 

 in all respects like the compound which we were formerly led to regard as a com- 

 pound formed by combination of casein and an acid and which we regarded as a 

 casein mono-salt of the acid precipitant. 



"When 1 gram of base-free casein is treated with about 0.5 CC of /'„ hydrochloric 

 acid, a substance is formed which is insoluble in warm 5 per cent salt solution and 

 in hot 50 per cent alcohol and which is no Longer plastic or ductile on warming. 

 This is like the substance usually formed when milk coagulates by natural souring. 

 By treating base-free casein with dilute acid, it was found that 1 gram of base-free 

 casein appears to combine withabout 0.5 cc of t " hydrochloric acid, forming a casein 

 salt of hydrochloric acid. While the compounds formerly regarded by us as casein 

 mono-salts of acids have been shown by us to be identical with base-free casein, the 

 compounds which we called casein di-salts of acids are compounds formed by com- 

 bination of acids with free casein. 



"A preparation of base-free paracasein was made, and from this dissolved in lime- 

 water were prepared ( 1 I basic calcium paracasein, containing in combination about 

 2.40 per cent of calcium oxid, and (2) neutral calcium paracasein containing about 

 1.50 per cent of combined calcium oxid. 



