254 DAIRY TECHNOLOGY 



point of milk is a little higher than that of water, viz., 

 about 2i4F. At such a temperature, during so long a 

 time as is necessary for evaporation, the milk assumes a 

 marked cooked flavor, and some natural characteristics 

 of the milk components change. For instance, the sugar 

 caramelizes, the fat melts into oil so as to make remixing 

 difficult, some albumen coagulates, and a portion of the 

 calcium phosphate salts separates from the casein. If the 

 atmospheric pressure is reduced so as to bring the boiling- 

 point to from 120 to 130 F., evaporation takes place and 

 the undesirable changes incident to higher heat are absent. 

 This is effected in the apparatus known as a vacuum pan. 

 Such a pan consists usually of four chief parts : 



1. The pan or kettle, which holds the milk and which 

 is usually lined with bright copper. 



2. A steam jacket, around the pan or steam coils, or 

 both, to supply the heat necessary for evaporation. 



3. The condenser, connecting with the top part of the 

 pan for condensing the steam and creating additional 

 vacuum. Cold water constantly circulates through the 

 condenser. 



4. The vacuum pump, used for reducing the atmospheric 

 pressure in the pan by pumping out the air and for remov- 

 ing steam and water in case a wet vacuum is used. If 

 a dry vacuum is used, the pump removes only the air, 

 and the water flows out by its own gravity. 



So far as known, Mr. Gail Borden of the United States 

 was the inventor of the vacuum method of milk conden- 

 sation. A patent was taken out by him in the United 

 States in 1856. One objection to this first condensed 

 milk was that it would keep only a few weeks. 



Mr. C. A. Page, then United States consul at Zurich, 

 improved the Borden method by adding sugar. This 



