SWEETENED CONDENSED MILK CONDENSING 95 



use in the condenser. Under average conditions about fifteen 

 pounds of steam pressure may be safely used. 



During the early stages of the pro-cess, when the milk is of 

 low density, the evaporative duty is high, probably about twenty- 

 five to thirty-five pounds per square foot of heating surface with 

 ten pounds of steam pressure. This gradually decreases and is 

 lowest toward the end of the process. 



When enough milk is in the pan to completely cover the 

 jacket and coils, the milk intake should be reduced and regulated 

 in accordance with the rate of evaporation.- The milk is drawn 

 into the pan continuously, but only as fast as it evaporates. It 

 should be kept as much as possible at a constant level, and this 

 level is preferably as low as is consistent with complete covering 

 of the upper most coil. 



In order to secure maximum rapidity of evaporation, the 

 vacuum pump should run at the proper speed and its operation 

 should be uniform, a uniform vacuum and temperature should 

 be maintained and the milk should be prevented from rising to 

 an abnormally high level in the pan. 



- Prevention of Accidents. The operator should pay strict 

 attention to the pan in order to avoid loss of milk due to acci- 

 dents. He should watch the water supply and govern its use 

 accordingly. If the water supply becomes exhausted, air is liable 

 to be drawn into the pan through the condenser. This will cause 

 the milk to drop suddenly and then rise in a body, threatening 

 to escape through the condenser. Whenever air in considerable 

 quantities is allowed to enter the pan while in operation, be it 

 as the result of lack of water, or through any other cause, or 

 when the vacuum pump is allowed to stop and live steam is 

 turned into the milk in the pan, as is the case when the milk 

 is superheated, the escape of milk may be avoided by immediately 

 shutting the steam inlet to the jacket and coils, by closing the 

 milk intake and by slightly opening the blow-down valve when- 

 ever the milk rises dangerously high. By skillful manipulation 

 of the blow-down valve until the milk again settles down to 

 uniform boiling, loss can be avoided and the process can be con- 

 tinued in the normal way. 



