Condensed Milk and Milk Powder ioi 



It is advisable, however, to heat this milk only to about 150 to 

 160 degrees F. in order to secure a nice "liver" (coagulum), when 

 it is superheated in the pan. If the milk is heated to the boiling 

 point in the forewarmers, it does not respond to the superheating in 

 the pan as satisfactorily. 



Condensing. — The condensing of plain condensed bulk milk is 

 done in the vacuum in a similar manner as described under evapo- 

 rated milk, except that the evaporation is carried farther. 



Superheating. — When the condensation is nearly completed the 

 milk in the pan is superheated. This is accomplished by shutting 

 off the steam to the jacket and coils, closing the valve that regulates 

 the water supply of the condenser, stopping the vacuum pump and 

 blowing steam direct into the milk in the pan, for the purpose of 

 swelling and thickening it. During this process the vacuum drops to 

 about six inches of the mercury column and the temperature rises 

 to between 180 and 200 degrees F. When the milk has become 

 sufficiently thick or, in the language of the processor, has produced 

 the "proper liver" (coagulum) the steam is shut off, water is again 

 turned into the condenser and the vacuum pump is started up. As 

 soon as the vacuum has risen to twenty-five to twenty-six inches 

 and the temperature has dropped to aibout 130 degrees F. the pro- 

 cess is complete, the vacuum is released and the condensed milk is 

 .drawn off. The superheating occupies about twenty-five to thirty 

 minutes. 



Striking. — The striking, or sampling and testing for gravity is 

 done with the same Beaume hydrometer that is used for evaporated 

 milk. The batch should be struck before and after superheating. 



Ratio of Concentration. — The ratio of concentration varies 

 largely with the fat content of the milk, although the locality and 

 season of year are also influencing factors. Whole milk is con- 

 densed at the ratio of about three parts of milk to one part of con- 

 densed milk, while the ratio of concentration for skim milk is about 

 4 to 1. The proper density varies somewhat with locality and 

 .■reason of year. Roughly speaking, whole milk has reached the 

 proper density when the Beaume reading at 120 degrees F. is about 

 10 degrees B. and skim milk has reached about the proper density 

 when the Beaume reading at 120 degrees F. is about 14 degrees B. 



