126 Evaproratkp M1LK—HoMocENIZING 
finer the opening, the faster the milk travels through the orifices 
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 constituents 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 and 
reliable homogenizer 
are: A high class, high 
pressure, sanitary milk 
pump, a-_ resistance 
valve or similar homo- 
venizing arrangement 
made from material 
which will not wear nor 
rust, and a means for 
accurately adjusting 
: Fig. 47. The Gaulin homogenizer 
this valve. Courtesy of Creamery Package Mfg. Co. 
