EVAPORATED MILK STERILIZING 123 



posure so long, as to cause the formation of a hard, unshakable 

 curd and dark color. 



Some processors use a very short process with high tempera- 

 tures, 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 necessary to 

 keep the fat from separating in storage. The author's judgment 

 in this matter is, that it is not safe to raise the temperature 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 the formation of too firm a curd. Where 

 the maximum temperature to which the milk is raised in the 

 sterilizer is 230 degrees F. or thereabout, the raise of the last ten 

 degrees should occupy from thirty-five to forty-five minutes, and 

 this time should be about evenly distributed over the last ten 

 degrees. 



Of recent years, the practice of stopping the reel of the 

 sterilizer, either at intervals or when the maximum temperature 

 has been reached, has been. adopted by some of the manufacturers. 

 In this case, the temperature usually is rapidly raised to about 

 240 F., and after keeping the reel running at this temperature 

 for a few minutes (about two minutes) the reel is stopped and 

 this temperature is maintained for from 15 to 20 minutes, with 

 the cans laying still. When the "hold" is completed, the cooling 

 proceeds in the usual way. Some condenseries stop the reel for 

 several minutes once or twice when the temperature has been 

 lowered and before it has dropped to below 212 F. 



This method of sterilizing, by stopping the reel, has the 

 advantage of developing in the cans a soft, custard-like coagu- 

 lum, giving the product a very heavy consistency and making it 

 appear rich and creamy. It represents a form of superheating, 

 however, which if not done with great care, may prove disastrous, 

 causing the evaporated milk to spontaneously thicken and become 

 cheesy in consistency upon storage. 



In his efforts to insure complete sterility the operator should 

 understand that the size of the cans may influence the sterilizing 

 efficiency. It takes more time and agitation to sterilize gallon 

 cans than small cans. At a time of the year when the milk con- 

 tains micro-organisms of relatively high resistance to heat, as 



