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The Different Methods of Estimating Protein 



in Milk. 



George Spitzer. 



It is often desirable to estimate the proteids in milk other than the 

 official method. This is especially true in cheese factories where it is desirable 

 to know the percent of casein in milk, since it is the casein in milk that gives 

 it its nutritive value, as far as the proteins are concerned. It is frequently 

 desirable to know the protein content in milk for infant and invalid feeding. 

 With the present method of determining the fat by the Babcock method, 

 which is quite accurate and can be done in all creameries, a rapid method 

 for estimating the percent of casein and fat in milk gives us the necessary 

 data to control the ratio of casein to fat in milk for feeding. Frequently a 

 chemist is requested to determine the fat and casein in human milk where 

 a physician has reason to beleve that there exists an unbalanced ratio of fats 

 and proteids. 



There are three methods for rapid estimation of casein or proteids in milk, 

 all of which possess merits worthy of consideration and could be used in a 

 great many laboratories that, are equipped with the apparatus necessary to 

 determine the proteids by the official method. Although such equipment 

 is at hand, when only a few determinations are to be made, the methods 

 reviewed in this paper save time and the results obtained are sufficiently 

 accurate. For the volumetric estimations of milk proteids, two standard 

 volumetric solutions are required, besides a few beakers and flasks, apparatus 

 found in any laboratory, or if one wishes to fit up for this purpose only, the 

 expense is quite nominal. 



In discussing the different methods, the order in which they are taken up, 

 is no indication of their priority. Since 1892 various attempts have been made 

 in devising a volumetric method for the estimation of casein in milk, but 

 most were unsatisfactory, either owing to the extensive equipment or to the 

 complicated indirect methods used. The main characteristics that a method 

 should possess are: first, it should be accurate; second, it should require only 

 a short time in making an estimation; third, the apparatus should be simple; 

 fourth, materials and apparatus used should be easily obtainable. 



