124 EVAPORATED MILK HOMOGENIZING 



tailed directions on calculations of concentration and on exact 

 method for standardizing-, the reader is referred to Chapter 

 XXIX on "Standardization." 



CHAPTER IX. 

 HOMOGENIZING. 



Purpose. The object of homogenizing is to avoid the separa- 

 tion of the butterfat in the evaporated milk after manufacture. 



The butter fat is present in milk in the form, of minute 

 globules. These fat globules are lighter than the rest of the 

 ingredients of the milk. They, therefore, show a strong ten- 

 dency to rise to the surface and to form a layer of thick cream 

 in the cans. When these cans are subsequently subjected to 

 agitation, as is the case in transportation, this cream churns, 

 forming lumps of butter. This tendency of evaporated milk to 

 separate in storage and churn in transportation is especially 

 noticeable with milk rich in fat and in which the large fat glob- 

 ules predominate. In Jersey and Guernsey localities, it is more 

 difficult, therefore, to manufacture evaporated milk that does not 

 separate, than in Holstein and Ayrshire localities. While sepa- 

 rated and churned evaporated milk, is perfectly sound and in 

 every way as valuable as a food, as it would be without this 

 separation, it does not sell in this condition. It is rejected on 

 the market. 



This tendency toward fat separation can be minimized and 

 frequently entirely prevented by increasing the viscosity of the 

 evaporated miilk. This can be accomplished by superheating the 

 milk in the pan or after it leaves the pan, and by prolonging 

 the sterilizing process, raising the heat very slowly or stopping 

 the reel of the sterilizer at certain stages of the process. How'- 

 ever, there are conditions when even these precautions do 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 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 



