REPORT OF THE DEPARTMENT OF 

 CHEMISTRY. 



COMPOSITION AND PROPERTIES OF SOME 



CASEIN AND PARACASEIN COMPOUNDS 



AND THEIR RELATION TO CHEESE.* 



LUCIUS L. VAN SLYKE and ALFRED W. BOSWORTH. 



SUMMARY. 



1. Object. — The work was undertaken to obtain more informa- 

 tion regarding the compounds formed by casein and paracasein 

 with bases, especially with Ca. Two compounds have been previ- 

 ously prepared, one neutral to phenoiphthalein, containing 1.78 

 per ct. Ca (2.50 CaO), and the other, neutral to litmus, containing 

 1.07 per ct. Ca (1.50 CaO). Our main object was to learn if there 

 were other compounds containing less Ca. Another purpose was 

 to ascertain the composition of the substance formed in cheese 

 which is insoluble in water but soluble in 5 per ct. solution of Na CI. 



2. Method of preparing casein. — Casein must be made base-free 

 for use in such work. Preparations were made containing less than 

 0.1 per ct. of ash. The usual method was employed in part, pre- 

 cipitating separator skim-milk with dilute acetic acid, redissolving 

 the washed precipitate in dilute NH4OH, continuing precipitation 

 and solution three or more times. Finally, the remaining calcium 

 is precipitated from the ammonia solution as oxalate, the precipitate 

 being removed by centrifuging and filtering, and the filtrate pre- 

 cipitated with dilute HCl. After washing free from HCl, the casein 

 is treated with alcohol and ether, and after grinding and partial 

 drying is dried over H0SO4 under reduced pressure. Analysis of 

 such casein preparations agrees with the composition generally 

 accepted, except in the amount of phosphorus and sulphur. 



3. Preparation and composition of basic calcium caseinate. — The 

 compound was prepared in two ways, (i) by decomposing CaCOs 

 with casein and (2) by treating casein with a lime-water solution 

 and neutralizing the excess with HCl, with phenoiphthalein as 

 indicator. The composition of the resulting compound was deter- 

 mined (i) by weighing the CO2 expelled from CaCOa, (2) by 

 determining the Ca in the resulting casein compound and (3) by 

 analysis of compound formed by treating lime-water solution of 

 casein with acid until neutral to phenoiphthalein. The different 

 results agree closely, showing basic calcium caseinate to contain 

 about 1.78 per ct. Ca (2.50 CaO), or i gram of casein combines 

 with 9 X 10^ gram equivalents of Ca. 



"^ A reprint of Teclniical Bulletin No. 20, December, 1912, 



[309] 



