140 EVAPORATED M1uK—S'ERILIZING 
the sterilizer for heat distribution is to test numerous cans 
from different parts of the sterilizer, after sterilization, for vis- 
cosity by means of the Mojonnier viscosimeter or similar device, 
as described under ‘Testing Sample Cans for Viscosity,’ see 
this chapter, succeeding paragraphs. 
Temperature and Time of Exposure.—\\hen the sterilizer 
is filled with the cans and closed, the frame work is set in motion 
and steam is turned into the sterilizer. In order to hasten the 
heating and expel all the air, the exhaust and safety should be 
left open until the temperature has risen to 212 degrees F. This 
temperature is usually reached in about ten to fifteen minutes. 
The exhaust and safety are then closed. 
From this point on, the process must depend on locality, 
season of year and condition, properties and concentration of the 
milk. No formula can be laid down which can be depended on 
to give uniformly satisfactory results under all conditions. Nor 
does the proper sterilization depend on one particular formula. 
There are numerous ratios of temperature, time of exposure and 
extent of agitation, which when adjusted to local conditions may 
give satisfactory results. The temperature should be high enough 
and the duration of exposure long enough to insure absolute 
sterility of the product and to give the milk sufficient body to 
prevent the separation of the butter fat in subsequent storage. 
The temperature should not be so high nor the duration of ex- 
posure so long, as to cause the formation of a hard, unshakable 
curd and dark color. 
Some processers use a very short process with high tem- 
peratures, others raise the heat gradually and not to quite so high 
a degree. The more gradual heating is preferable. as it gives 
the product a better body and more viscosity, which is neces- 
sary to keep the fat from separating in storage. The author's 
judgment in this matter is, that it is not safe to raise the tem- 
perature to less than 230 degrees I*. and it is advisable to heat 
the milk to 234 to 236 degrees F.. provided that the milk is in 
condition to stand this heat without formation of too firm a 
curd. \Vhere the maximum temperature to which the milk is 
raised in the sterlizer is 230 degrees F. or thereabout, the raise 
of the last ten degrees should occupy from thirty-five to forty- 
