EVAPORATED MILK STERILIZING 125 



to be used for the entire batch in the large sterilizer may be 

 adjusted according to the behavior of the contents of the sample 

 cans in the pilot sterilizer. 



Qualifications of the Processer. The operator, or the person 

 directing the sterilizing process, should thoroughly appreciate 

 the complexity of the product, understand the cause and effect 

 of the many influencing factors, study the ever-changing condi- 

 tions and modify the process in accordance with prevailing con- 

 ditions. He should know that during the exceedingly hot sum- 

 mer days, when the cows suffer from heat and are pestered with 

 flies, the milk will not stand as much heat without badly curdling 

 in the sterilizer as under more favorable conditions. He should 

 know that toward and during the fall months the organisms 

 normally present in milk are more resistant and require higher 

 heat to be destroyed, than earlier in the season. 



Rapid and Uniform Cooling. As soon as the required heat 

 has been given the milk in the sterilizer, the steam should be 

 turned off and the exhaust and drain should be opened. When 

 the temperature has dropped to about 220 degrees F., cold water 

 should be turned into the sterilizer while the cans are constantly 

 in motion, until the cans are cool enough to handle. There should 

 be enough cold water available to reduce the temperature to 70 

 or 80 degrees F. in twenty minutes for gallons and in ten to 

 fifteen minutes for small size cans. The water pipe should be 

 so arranged as to distribute the water uniformly over the entire 

 length of the sterilizer. 



If the process is to be sucessful, the processor must have as 

 nearly perfect control of the heat as possible. This means espe- 

 cially, that there must be plenty of water available to insure 

 rapid cooling and the water must be distributed over the cans 

 uniformly. Insufficient water supply and uneven distribution 

 of the water in the sterilizer, means that some of the cans are 

 exposed to the sterilizing heat longer than others, causing lack 

 of uniformity in the smoothness and color of the milk of different 

 cans of the same batch. Delayed cooling, owing to insufficient 

 water supply, has the further disadvantage of causing the cans 

 to bulge badly, owing to the difference in pressure between the 

 interior and exterior of the cans. This is especially noticeable 

 in gallon-size cans, the ends of which may become badly dis- 



