MILK AND MILK PRODUCTS - 25 



casein and albumin is made by Sebelein's method, as follows: 

 20 c.c. of the sample are mixed with 40 c.c. of a saturated solu- 

 tion of magnesium sulfate and powdered magnesium sulfate 

 stirred in until no more will dissolve. The precipitate of casein 

 and fat, including the trace of globulin, is allowed to settle, fil- 

 tered, and washed several times with a saturated solution of 

 magnesium sulfate. The filtrate and washings are saved for 

 the determination of albumin. The filter and contents are 

 transferred to a flask and the nitrogen determined by the 

 method described above. The nitrogen so found, multiplied 

 by 6.38, gives the casein. 



The filtrate and washings from the determination of casein, 

 are mixed, the albumin precipitated by Almen's tannin reagent, 

 filtered, and the nitrogen in the precipitate determined as above. 

 The same factor is used. 



Alm&n's reagent is prepared by dissolving 4 grams of tan- 

 nin in 190 c.c. of 50 per cent, alcohol and adding 8 c.c. of acetic 

 acid of 25 per cent. 



In a mixture of milk and whey (prepared with rennet) in 

 about equal parts, Richmond and Boseley found about 0.3 

 per cent, of albumoses not precipitated by the copper sulfate 

 nor by magnesium sulfate, but precipitable, along with the 

 albumin, by a solution of tannin. The separation may be 

 effected by diluting the filtrate from the magnesium sulfate 

 precipitation, acidifying slightly with acetic acid, and boiling, 

 when the albumin will be coagulated and precipitated. The 

 albumoses may be separated by filtering the solution and pre- 

 cipitating with tannin solution. The precipitated proteids are 

 best estimated by determining the nitrogen in the moist preci- 

 pitate. The separation of the proteids may be effected, though 

 less accurately, by the use of acetic acid, as recommended by 

 Hoppe-Seyler and Ritthausen. 



The following are A. O. A. C. methods: 



i. Provisional Method jor the Determination of Casein in 



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