122 EVAPORATED MILK STERILIZING 



there be a free air space between every two layers of cans, so as 

 to allow the steam to circulate freely and to come in direct con- 

 tact with every can. When the cans are piled into the sterilizer 

 six to twelve layers deep without any free air space between 

 layers, the cans in the center do not receive as much heat as those 

 at the sides, ends, top and bottom. This causes irregular heating 

 and imperfect sterilization. 



A satisfactory means of insuring even distribution of heat 

 is to fill the sterilizer about one-thirdful of water, so that, when 

 the sterilizer is in operation the cans pass through this water, 

 with each revolution of the frame work. Water distributes the 

 heat uniformly, rapidly and there is no danger of the formation 

 of air pockets between the cans. Since the heat is applied by 

 steam under pressure the temperature of the water is equal to 

 that of the steam in the sterilizer. This precaution is especially 

 necessary in the case of baby-size cans (eight ounces) which are 

 usually piled in stacks more than two deep. When sterilizing 

 in the absence of water there is danger of lack of uniformity of 

 the amount of heat they receive. 



Temperature and Time of Exposure. When 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- 



