430 EXPERIMENT STATION RECORD. 



tho estimation of oasoin monolactate and casein dihu'tate which were 

 adopted provisional!}' by the association. The report of R. Harcourt, 

 associate referee on vegetable proteids. was not ready for presenta- 

 tion, but by vote of the association will be included in the proceed- 

 ings. It was announced that this report would consist largel}' of 

 compiled matter. W. 1). Bigelow, as associate i-eferee on meat proteids, 

 called attention to the comparisons made by H, S. Grindley of the 

 amounts of proteids in the water extracts of raw and cooked meats 

 precipitated b}- various reagents, and reported investigations made b}^ 

 himself and F. C. Cook during the year. 



In the examination of meat proteids the association recommended 

 that further trial be made of phosphotungstic acid alone in hot and 

 cold solutions, phosphotungstic acid followed ])v bromin, phospho- 

 tungstic acid followed by zinc sulphate, and tannin and salt followed 

 bj" zinc sulphate; and that precipitation by bromin alone and b}' 

 bromin in the filtrate from zinc sulphate be discontinued. The work 

 b}" Dr. Grindley is noted below, as is also a paper on the determina- 

 tion of gliadin and glutenin which Avas presented in this connection. 



Report of referee on milk and cheese proteids, L. L. Van Slyke. — A prelim- 

 inary report was made upon a study of the official method for the determination of 

 casein in milk, explanations being offered for some of the reactions met with in the 

 use of that method. It was believed that the official method could be improved, 

 and the referee announced that the results of the completed investigation along this 

 line would be ready for presentation another year. 



A study was made of the relation of casein monolactate and casein dilactate to the 

 Hess and Doolittle method of detecting process or renovated butter. It was pointed 

 out that the characteristics of the curd upon which this test is leased depend upon 

 the presence of one or the other of these compounds, and furthermore, that these 

 compounds are dependent upon the amount of acid produced in the ripening of the 

 cream. It was found possible to make genuine butter which would respond to the 

 Hess and Doolittle test for process butter or vice versa, and also that different reac- 

 tions could be obtained with butter when fresh and when several weeks old. It was 

 believed, therefore, that the test must be regarded as worthless. 



The methods devised by the referee and E. B. Hart for the separation and estima- 

 tion of casein, casein monolactate, and casein dilactate in milk are given below in 

 the form presented: (1) Dderw'ination of casein monolnrtale hi milk. Casein mono- 

 lactate in milk coagulates readily at -10° C. Hence, in a milk containing only casein 

 and casein monolactate, the monolactate can be separated by heating the milk to 

 about 40° C, filtering the precipitate formed, washing, and determining the nitrogen 

 in the precipitate. Ten gm. of milk diluted with 90 cc. of water give good results. 

 (2) Separation of casein monolactate and casein dilactate. Casein dilactate coagulates 

 completely at 40° C. and below. In milk containing casein mono- and dilactates, we 

 heat 10 gm. of milk diluted with 90 cc. of water to 40° C, and these two salts precipi- 

 tate and are separated from the milk casein 1)y filtration. The washed precipitate 

 is then treated with 100 cc. of a 5 per cent solution of sodium c-hlorid and the whole 

 heated to 55° C. with frequent agitation for 2 hours. The process is facilitated some- 

 what ])y the presence of pure quartz sand. The casein monolactate goes into solution 

 and is separated from the casein dilactate by filtration and washing. (3) Separa- 

 tion and determination of casein, casein vwnolactate, and casein dilactate in mill:, (a) 

 The total amount of nitrogen precii^itated by acid is determined by the official method 



