64 Condensed Milk and Milk Powder 



The smaller the difference in temperature between the con- 

 denser discharge and the vapors in the pan, the more economic is 

 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 no 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 Chapter 

 V, on the "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. 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 automatically 

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

 covers the jacket, steam is gradually turned into the jacker;. 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 consider- 

 able 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 



