98 MILK 



65.6° C. 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. 



Lactoglobtjlin 



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 MgS04, redissolved, precipitated with NaCl, 

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

 belein). 



2. Colostrum is warmed to 40° C. and saturated with aliim. 

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

 The last filtrate is saturated with MgS04 and NaCl, the precipi- 

 tate dissolved and dialyzed, and finally precipitated with nitric 

 acid and alcohol (Tiemann). 



Lactoglobuhn is probably identical with serum globulin. It 

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

 tated by MgS04 and (NH4)2S04. 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 gelatinous 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 solul)le. 

 Heated with HCl 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, galactoz5mie, 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 



