EVAPORATED MILK HOMOGENIZING 125 



force, they cannot rise to the surface and therefore 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 earlier theories concerning the action of the homogen- 

 izer were that the milk had to pass through openings so mi- 

 nute, that the fat globules, in order to be able to pass through, 

 were crushed, torn and divided into much smaller units, hence 

 their fine state of division in the homogenized milk. 



Later study of the principles of homogenization has revealed 

 facts and probabilities which do not bear out the earlier assump- 

 tions. Men who have subjected the construction and operation 

 of homogenizers to intensive study claim, that the openings or 

 orifices through which the milk passes in the machines in com- 

 mercial use when operating at capacity, range in size from about 

 .003 inch to .01 inch. If these findings are correct, then it is ob- 

 vious that .the fat globules and even clusters of fat globules can 

 pass through the homogenizer as entire units and without being- 

 broken up, for the average fat globule measures about .0001 inch 

 in diameter. 



It is not improbable that the homogenizing action is very 

 similar in its atomizing cause and effect, as that which takes 

 place in the spray-drying process, only the homogenizing action 

 is more intensive because of the smaller size of the openings 

 through which the milk must pass. The atomized spray in 

 the spray-drying process is formed, not in the spray nozzle, but 

 as soon as the pressure is released, or- as soon as the milk 

 escapes from the nozzle. 



In the case of the spray-drying process, the atomized spray 

 is discharged into a medium of heated air, while in the homogen- 

 izing process, the atomized spray is discharged into a liquid 

 medium, milk. 



The degree of fineness of the atoms in either case depends 

 on the speed with which the liquid passes through the orifice ; 

 the higher the speed the finer and more minute the atoms. And 

 the speed of passage in turn depends on the degree of pressure 

 and the size of the orifice. The greater the pressure" and the 



