158 MARKET DAIRYING 
to 150° F., and hold at this temperature for 15 minutes. 
Then quickly cool and keep the cream as near freezing 
temperature as possible for at least 24 hours before 
freezing. Holding the pasteurized cream cold this length 
of time restores to a great extent the viscosity which it 
has lost in the pasteurizing process. 
Cream can also be satisfactorily pasteurized in con- 
tinuous pasteurizers, but greater care is necessary because 
of the higher temperature that must be employed. But 
even with the higher temperature the pasteurizing is 
bound to be less thorough than where the cream is held 
some time at a lower temperature. 
Freezing Process. With an initial temperature of 
about 35° F., the time required to freeze ice cream should 
average about twelve minutes, and to get the best con- 
sistency the temperature at the close of the freezing 
process should be approximately 28° F. 
Too quick freezing causes the water to separate from 
the cream, which results in a granular ice cream. Freez- 
ing too slowly reduces the overrun and tends to make the 
ice cream smeary. 
To reduce the temperature of a mass of cream below 
the freezing point, requires a freezing mixture of a low 
temperature. Such a mixture is secured by mixing salt 
and crushed ice in the proportion of one of salt to about 
twelve of ice. The purpose of the salt is to lower the 
freezing point of the melting ice and to hasten the melt- 
ing. 
To melt one pound of ice at 32° F. into water at the 
same temperature requires 142 heat units. Rapidly melt- 
ing ice, therefore, absorbs a large quantity of heat which 
in the freezing of cream is largely extracted from the 
cream. 
