304 THE MILK QUESTION 



Diminution of the organic phosphorus. 



Increase of inorganic phosphorus. 



Precipitation of the calcium and magnesium salts and 

 the greater part of the phosphates. 



Expulsion of the greater part of the carbon dioxide. 



Caramelization or burning of a certain portion of the 

 milk sugar (lactose), causing the brownish color. 



Partial disarrangement of the normal emulsion and 

 coalescence of some of the fat globules. 



Coagulation of the serum albumin, which begins at 75° 

 C. 



The casein is rendered less easy of coagulation by rennin 

 and is more slowly and imperfectly acted upon by pepsin 

 and pancreatin. 



Boiling gives the milk a "cooked" taste. 



The cream does not rise well, if at all. 



When the milk reaches about 60° C, a scum forms on the 

 surface which consists of — 



Fatty matter 45.42 



Casein and albuminoid 50.86 



Ash 3.72 



Milk heated in closed vessels does not form a pellicle 

 even when the temperature reaches 100° or 110° C. Milk 

 heated in the open air, after cooling forms a pellicle on the 

 surface which renews itself if it is removed. It seems that 

 this pellicle is due mainly to the drying of the upper layer 

 of the liquid. 



Heat kills the ferments in milk,^ which according to some 



1 Hippius {Deut. med. Woch., vol. 27, 1901, pp. 481, 502) states that 

 the oxidizing ferments are able to withstand temperatures between 60° 

 and 65° C. for a long time, but are destroyed after a short exposure to 

 76° C. The lipase, or fat-splitting ferment, withstands one hour's heating 

 at 60° C, or 62° for a short time; is weakened at 63°, and destroyed at 

 64° C. The proteolytic ferment withstands one hour's heating at 60° or 

 half an hour at 65° C. The amylase withstands one hour at 60° and 

 is only destroyed at 75° C. See also Kastle and Roberts, article no. 10, 

 p. 307, Hyg. Lab. Bui. no. 41, P. H. & M. H. S. 



