Sweetened Condensed Milk — Condensing 85 



the use of the water and vice versa. It is not advisable under aver- 

 age 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 eighteen to twenty-five pounds of water. The quan- 

 tity of heating steam 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 condensed, there is 

 great waste of fuel. For further details on this point see "Descrip- 

 tion 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 man- 

 hole 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 pah automatically 

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

 coVfers 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 grad- 

 ually increased until it reaches the maximum. The maximum pres- 



