Evaporated Milk — Homogenizing 



111 



ever, there are conditions wlien even these precautions do not 

 permanently avoid separation of the fat. In such cases, the 

 proper use of the homosirenizer furnishes a reHable means to 

 guard against this difficulty. 



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

 genizer is to force the milk under high pressure through exceed- 

 ingly small, microscopic openings. By so doing the fat globules 

 are broken up so finely that they fail to respond to the gravity 

 force, they cannot rise to the surface and iherefore remain in 

 homogeneous emulsion. The value of the homogenizer lies in 

 removing the fundamental cause of this separation. It reduces 

 the fat globules to such small size that their buoyancy, or grav- 

 ity force, is not great enough to overcome the resistance of the 

 surrounding liquid. 



The tendency of fat globules to separate out in homogenized 

 evaporated milk is further reduced by the fact that the homogen- 

 izer also alters the physical condition of the casein, making it 

 more viscous and thereby increasing the resistance wdiich the 

 fat globules must overcome in their upward passage. 



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

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



and the "Progress' 



homoeenizer. 



Fig. 38. The Progress homogenizer 

 Courtesy of Davis- V^^atkins Dairymen's Supply Company 



In the Gaulin 

 homogenizer, the 

 milk is forced, by 

 means of single- 

 acting pumps, a- 

 gainst an agate 

 valve which pres- 

 ses against a 

 ground valve seat. 

 The milk has to 

 pass between the 

 ground surfaces of 

 this valve and 

 valve seat. This 

 causes the fat 

 globules to be di- 



