553 



Little change, if any, occurs in the chemical constitution of the 

 fats, and cream can be heated to a higher temperature than milk 

 before the cooked flavour is produced. The small groups or clusters 

 of fat globules which are found in fresh milk are largely disinte- 

 grated into separate globules by heating, and the cream, which 

 rises slowly, is thin. 



The milk sugar is slightly oxidized, and acids are split off from 

 it, the alkaline phosphates of the serum assisting the change ; the 

 milk becomes distinctly acid if it is boiled for three or four hours, 

 and yellowish or brownish in colour, the altered tint, however, 

 being more likely due to alteration in the proteins than in the 

 sugar. 



Very striking changes are made in the proteins of the milk by 

 heating. The soluble albumin becomes coagulated and probably 

 decomposed to some extent with the evolution of a small quantity 

 of sulphuretted hydrogen at temperatures from 70 C. to too C. 

 The pellicle or skin which torms when milk is heated in an open 

 vessel consists of coagulated albumin and dried caseinogen, with 

 fat and other constituents also. 



The power of curdling by rennet and acids is very much re- 

 duced, a point of great importance to the cheese-maker. For the 

 coagulation of the caseinogen more rennet is required and the curd 

 is too crumbly and soft for the manufacture of hard pressed cheeses. 

 The altered character of the caseinogen appears to be chiefly con- 

 nected with the precipitation of insoluble calcium phosphate, and 

 although some improvement in the curdling property can be made 

 by the addition of dissolving agents such as carbon dioxide, hy- 

 drochloric and other acids, or by the addition of soluble calcium 

 salts, no really characteristic Cheddar, Cheshire, or other hard 

 cheese has yet been made from strongly heated milk. 



As stated previously heating destroys the normal enzymes of 

 milk. There is little doubt that the coagulation of the albumen, 

 the changes in the solubility of the casein and calcium salts, and 

 the destruction of the enzymes render the milk less digestible and 

 reduce its nutritive qualities. " 



A Prize for Experimental Work on Milk. The Farmer and 

 Stockbreeder. London, 18 July 1910. 



The International Dairy Federation bave established a prize for 

 the best work on a subject to be selected. The subject for the 



