166 CONCENTRATED 



Jf held in the factory, it should be placed in a cold room or 

 should be otherwise protected against temperatures sufficiently 

 high to cause if to sour. When kept at -40 degrees F. or below 

 the danger from souring is largely eliminated. If transported 

 long distances during warm weather, it should be shipped in 

 refrigerator cars. 



CHAPTER XIII. 

 CONCENTRATED MILK. 



Definition. Concentrated milk is cow's milk, either whole 

 milk, or partly or wholly skimmed milk, condensed at the ratio 

 of three to four parts of fresh milk to one part of concentrated 

 milk. It is not condensed in vacuo, but in open vats by passing 

 currents of hot air through the milk. It is sold largely in pint 

 and quart bottles for direct consumption. It is not sterile and 

 therefore keeps for a limited time only. Its keeping quality is 

 similar to that of a high grade of properly pasteurized milk. The 

 process by which the concentrated milk is manufactured is 

 known as the "Campbell Process." This process was invented 

 by J. H. Campbell of New York City, in 19CO and patented in 

 1901. 



Apparatus Needed. The principal parts are: the evapo- 

 rating vat with hot water jacket and coils, and air blast regis- 

 ters or nozzles near the bottom of the vat; an air blower which 

 furnishes the air blast; an air heater through which the air 

 blast passes and from which the heated air is conducted into the 

 milk; a water pump circulating hot water through the jacket 

 and coils; an auxiliary evaporating tank for completing the 

 evaporation ; and a spray pump which throws the spray of milk 

 drawn from the bottom of the main evaporating vat into the 

 auxiliary tank and for transferring the partly condensed milk 

 from tank 1 to tank 2. 



Operation of Campbell Process. The milk is heated to about 

 ICO degrees F. and allowed to flow into evaporating tank 1. 

 Water at temperatures ranging from 100 to 125 degrees F. is 

 forced through the coils and jacket. Hot air is then passed into 

 the milk. The temperature of the air is regulated so as to keep 

 the temperature, of the evaporating milk down to 120 degrees F. 



