94 SWEETENED CONDENSED MILK CONDENSING 



average conditions to so operate the pan that the temperature 

 of the condenser discharge drops below 110 degrees F., because 

 of the wasteful use of water under such conditions. 



The condensing of one pound of milk requires about one 

 pound of steam and ten to twenty-five pounds of water. The 

 number of heat units used for condensing in vacuum is practically 

 the same as that required by evaporating in open pans. In order 

 to use the steam economically the pan should be so operated as 

 to make possible its complete condensation by the time it leaves 

 the jacket and coils, Whenever so much steam is used that it 

 blows through and out of the jacket and coils without being con- 

 densed, there is great waste of fuel. For further details on this 

 point see "Description of the Vacuum Pan." 



Starting the Pan. Before drawing the milk into the pan, the 

 pan should be thoroughly rinsed with water, then steamed until 

 the temperature rises to about 180 degrees F. or above. Then 

 the manhole cover is put in place, all the air valves are closed, 

 water is turned into the condenser and the vacuum pump is 

 started. When the vacuum gauge shows over twenty inches of 

 vacuum, the pan is ready for the milk. 



Operating the Pan. The valve of the milk pipe leading to 

 the pan is now partly opened. The milk enters the pan auto- 

 matically as the result of the reduced pressure in the pan. When 

 the milk covers the jacket, steam is gradually turned into the 

 jacket. As each coil becomes submerged in milk, the coils are 

 charged with steam. At no time should steam be turned on the 

 jacket and coils when they are not completely covered with milk, 

 as such action would cause the milk to stick to and burn on the 

 heating surface, the milk would assume a burnt flavor, it would 

 become permeated with black specks and the evaporation would 

 be retarded. On the start, but a few pounds of steam pressure 

 should be used in the jacket and coils, to avoid burning, owing 

 to the presence in the milk of considerable air. As the milk 

 becomes more concentrated and settles down to uniform boiling, 

 the steam pressure may be gradually increased until it reaches 

 the maximum. The maximum pressure permissible must be gov- 

 erned by the amount of heating surface, the capacity of the vacu- 

 um pump and the temperature and amount of water available for 



