140 EVAPORATED MILK STERIUZING 



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. \Yhen the sterilizer 

 is rilled 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 fornmila. 

 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 F. 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. Where 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- 



