98 MILK 



65.6 G. 5.71 per cent, are coagulated; at 68.3 C. 12.76 per cent, 

 are coagulated, and at 71.1 C. 30.87 per cent, are coagulated. It 

 is usually stated that lactalbumin coagulates at 70 C., but that 

 coagulation is not complete at this temperature. 



LACTOGLOBULIN 



Lactoglobulin is obtained from milk by the following methods: 



1. Milk is saturated with NaCl, filtered, and the filtrate 

 warmed to 35 C. to remove remnants of casein. The filtrate is 

 then saturated with MgSO 4 , redissolved, precipitated with NaCl, 

 and finally dialyzed. Flakes of globulin are precipitated (Se- 

 belein). 



2. Colostrum is warmed to 40 C. and saturated with alum. 

 It is then filtered, the filtrate neutralized, and filtered again. 

 The last filtrate is saturated with MgSO 4 and NaCl, the precipi- 

 tate dissolved and dialyzed, and finally precipitated with nitric 

 acid and alcohol (Tiemann). 



Lactoglobulin is probably identical with serum globulin. It 

 is soluble in NaCl solution, even when acidified, but is precipi- 

 tated by MgS0 4 and (NH 4 ) 2 SO 4 . It is also precipitated by 

 tannin, but is not coagulated by rennet. It coagulates at 72 C. 

 Colostrum contains relatively large amounts of globulin, while 

 normal milk contains only traces of it. It is believed to be the 

 carrier of antibodies in milk. 



MUCOID PROTEIN OR LACTOMUCIN 



Mucoid protein can be prepared from butter, sweet butter- 

 milk, or cream by shaking with a mixture of 1 part alcohol and 

 2 parts ether. A gelatirjous precipitate appears when the mix- 

 ture has stood for some time. The precipitate is gathered and 

 washed with alcohol and^ ether mixture, and finally dried at low 

 temperature. 



Mucoid protein is a bulky, grayish- white hygroscopic powder; 

 it is insoluble in ammonia, acetic acid, and dilute mineral acids. 

 It swells in weak alkalies, only a small amount of it being soluble. 

 Heated with HC1 it yields a substance which reduces Fehling's 

 solution. 



OTHER PROTEINS IN MILK 



Minute amounts of the following proteins have been found 

 in milk: Albumose, lactoprotein, galactozyme, and opalisin. The 

 actual existence of these proteins is doubted by many inves- 

 tigators, and it must be admitted that there are sources of 

 error possible. Colostrum contains a large amount of albumin 



