24 MANUAL OF MILK PRODUCTS 



lactoglobulin, galactin, fibrin (trace), 0.2 per cent; total 3.8 



per cent. 



Casein. 



This is the most abundant of the albuminoids. It forms 

 about 3 per cent of normal cow's milk and about 80 per cent 

 of the "proteins. Kirchner gives the percentage composition 

 of casein as carbon 53.0; hydrogen 7.12; nitrogen 15.65; 

 oxygen 22.6 ; sulfur 0.78, phosphorus 0.85. Casein occurs in 

 milk in suspension, is insoluble in water, but is soluble in dilute 

 alkalies and in strong acids and can be separated from the sol- 

 uble constituents of milk-serum by means of a porous porcelain 

 filter. Pure casein is a white, odorless, tasteless substance, 

 and is the chief constituent in milk curd. It is coagulated by 

 acid, as in the case of souring milk, or by rennet, as in the 

 making of cheese. 

 Albumin or lact-albumin. 



Normal milk contains about 0.6 per cent of albumin which 

 forms about 15 per cent of the total proteids. It resembles 

 the albumin of eggs and that found in the blood ; is soluble in 

 water and is not coagulated by dilute acids or rennet, but is 

 coagulated by temperatures of 70-75 C. 

 Lactoglobulin. 



This is a protein which occurs in normal cow's rnilk only in 

 traces, but may be much more abundant in colostrum. It 

 appears to be the same as the globulin in blood-serum, being 

 coagulated by temperatures of 67-76 C. Lactoglobulin 

 occurs in milk partly in solution and partly in suspension or 

 colloidal solution. 

 Galactin. 



This substance has been found by different workers to exist 

 in milk in amounts approximating 0.1 per cent. Richmond 

 says, "This is essentially lacto-protein, perhaps contaminated 

 with some organic salts, and has no real existence in milk, 

 being portions of the casein and albumin which had escaped 



