Condensed Milk and Mii,k Powder 



87 



rated milk. This can be accomplished by superheating the milk in 

 the pan and by prolonging the sterilizing process, raising the heat 

 very slowly. However, there are conditions when even this pre- 

 caution does not permanently avoid separation of the fat. In such 

 cases, the proper use of the homogenizer furnishes a reliable means 

 to guard against this difficulty. 



Principle of the Homogenizer. — The principle of the homogen- 

 izer is to force the milk under high pressure through exceedingly 

 small, microscopic openings. By so doing the fat globules are broken 

 up so finely that they fail to respond to the gravity force, they can- 

 not rise to the surface and therefore remain in homogeneous emul- 

 sion. The value of the homogenizer lies in removing the funda- 

 mental cause of this separation. It reduces the fat globules to such 

 small size that their buoyancy, or gravity force, is not great enough 

 to overcome the resistance of the surrounding liquid. 



Kinds of Homogenizers. — There are at this time two makes of 

 homogenizers in use in this country, namely, the "Gaulin" and the 

 "Progress" homogenizer. 



In the Gaulin homogenizer, 

 the milk is forced, by means of 

 single-acting pumps, against an 

 agate valve which presses against 

 a ground valve seat. The milk 

 has to pass between the ground 

 surfaces of this valve and valve 

 seat. This causes the fat glob- 

 ules to be divided very minutely. 

 This type of homogenizer has 

 not been used much as yet in the 

 manufacture of evaporated milk 

 and but little is known concern- 

 ing its effect on this product. 

 In the Progress homogenizer the homogenizing principle con- 

 sists of forcing the milk, by means of single acting pumps, between 

 a series of discs with ground surfaces. The discs lay flat one upon 

 the other, they are enclosed in a cylinder and are held in place by a 

 rod running through their center. The discs are pressed against 

 each other by a heavy spiral screw, which regulates the pressure to 



Fig. 33. The Progress homogenizer 



Courtesy of 

 Dairy Machinery & Construction Co. 



