102 Condensed Milk and Milk Powder 



If the ratio of concentration exceeds 4:1 there is danger of gritty 

 milk, due to the precipitation of crystals of milk sugar. 



Cooling. — The plain condensed bulk milk is drawn into 40-quart 

 cans, placed in cooling tanks as described in Chapter VI, under 

 "Cooling of Sweetened Condensed Milk," and cooled to as near 

 the freezing point as facilities will permit. The product is then 

 ready for the market. If held in the factory, it should be placed in 

 a cold room or should be otherwise protected against souring. If 

 transported long distances it should be shipped in refrigerator cars. 



CHAPTER XIV 

 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 con- 

 centrated milk is manufactured is known as the "Campbell Process." 

 This process was invented by J. H. Campbell of New York City, in 

 1900 and patented in 1901. 



Apparatus Needed. — The principal parts are: the evaporating 

 vat with hot water jacket and coils, and air blast registers or noz- 

 zles near the bottom of the tank; 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 cir- 

 culating hot water through the jacket and coils ; an auxiliary evap- 

 orating tank for completing the evaporation ; and a spray purnp 

 which throws the spray of milk drawn from the bottom of the main 

 evaporating vat into that tank and for transferring the partly con- 

 densed milk from tank 1 to tank 2. 



Operation of Campbell Process. — The milk is heated to about 

 100 degrees F. and allowed to flow into evaporating tank 1. Water 

 at temperatures ranging from 100 to 125 degrees F. is forced through 



