EVAPORATED M11,.K—COoNDENSING 119 
pan must be relatively small. This milk foams more in the pan 
than the heavier sweetened condensed milk. This factor reduces 
therefore, the capacity of the pan. If the milk is not cooled upon 
arrival, but is transferred immediately to the hot wells. it is 
advisable to use numerous small wells, rather than but one or 
a few large ones. These small wells fill rapidly and the milk 
can be heated without delay. This system makes it possible to 
render the bacteria inactive and harmless practically as soon 
as the milk arrives, minimizing the danger of acid formation.? 
Steam may be saved if the milk is forewarmed by running 
it through coils inclosed in a chamber of exhaust steam, but the 
coils increase the labor and difficulty of cleaning. It is best to 
heat the milk to as near the boiling point as possible and hold 
it there for five to ten minutes. provided that the capacity of the 
factory warrants this delay. In this heating the casein ot the 
milk is somewhat changed. There occurs partial, though invis- 
ible, precipitation, and the higher the temperature to which the 
milk is heated, the more pronounced is this change. ‘This change 
is desirable, because the casein thereby surrenders, to a limited 
extent. its power and tendency to form a firm curd in the ster- 
ilizer. See also Chapter XI on “Sterilizing.” 
CONDENSING. 
The same apparatus, the vacuum pan and pump, is used 
for condensing the milk, and the process of condensing 1s prin- 
cipally the same, as in the case of sweetened condensed milk. 
The fresh milk is condensed at the ratio of two to two and one- 
half parts of fresh milk to one part of condensed milk. In some 
factories it is customary to superheat the milk in the pan before 
it is drawn off, i. e., the steam to the jacket and coils is shut off, 
the water valve is closed, the vacuum pump is stopped and 
“live’’ steam is passed into the condensed milk. When the 
vacuum has dropped to about six to eight inches, and the tem- 
perature has risen to 180 to 200 degrees F. the superheating is 
stopped, the steam is turned off, the vacuum pump is started 
again, and the condensing is completed. The superheating is fre- 
quently also done after the evaporated milk has been drawn 
1 See also Cooling Milk and Standardization. 
