126 



EVAPORATED MILK HOMOGENIZING 



finer the opening, the faster the milk travels through the orifice; 

 and in the case of the homogenizer, the finer the division of the 

 fat globules in the homogenized milk 



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 which the 

 fat globules must overcome in their upward passage. 



The exact changes which the casein undergoes are not well 

 understood, but it is not improbable that either the high pressure 

 or the vibration, or both, to which the milk is subjected in the 

 homogenizer, bring about a molecular rearrangement of the 

 casein. Possibly these factors cause the lactic acid which is 

 increased due to the concentration of the evaporated milk, to 

 remove calcium from the casein, leaving a part of the casein 

 as free casein which is a solid, and a part of the casein as casein 

 lactate which is in a colloidal state and which is readily hy- 

 drolized. 



The fact remains that, when the homogenizing is done un- 

 der relatively high pressure, or when done in a homogenizer 

 carrying a spring-loaded valve which tends to vibrate or pound 

 the constititents of the milk, the resulting homogenized milk 

 increases in thickness, is more susceptible to the curdling act- 

 ing of the heat in the sterilizer and is more prone to "feather" 

 or curdle when poured 

 into hot coffee. 



The essential fea- 

 tures of an efficient an.d 

 reliable homogenizer 

 are : A high class, high 

 pressure, sanitary milk 

 pump, a resistance 

 valve or similar homo- 

 genizing arrangement 

 made from material 

 which will not wear nor 

 rust, and a means for 

 a c c u r ately adjusting 



Fig-. 47. The Gaulin homogenizer 



this valve. Courtesy of Creamery Package Mfg. Co. 



