Condensed Milk and Milk Powder 



39 





A variety of methods and numerous different types of ma- 

 chines are used for this purpose in the' different milk condensing 

 factories. Some use large copper kettles in which the milk is heat- 

 ed' ; by turning steam direct into the milk. Others use jacketed cop- 

 per kettles equipped with a revolving agitator. The milk is heated 



by turning steam under pressure in- 

 to the jacket and the burning of the 

 milk is prevented by keeping the milk 

 in constant motion. Still others are 

 heating the milk by means of large 

 continuous pasteurizers of the Miller 

 type, in which case hot water serves 

 as the heating medium. The milk 

 passes in a thin layer between two 

 water-heated surfaces, one of which is 

 revolving. In some factories the milk 

 is forced through a series of pipes 

 inclosed in a hot water or steam 

 jacket. 



Finally, in some condenseries 

 a combination of the continuous 

 pasteurizer and the jacketed kettle is used. The milk is heated to 

 nearly the desired temperature in the pasteurizer. From there it 

 flows into the jacketed kettle. This kettle is so constructed that 

 when steam is turned into the jacket, the milk rises and it flows over 

 and off into the sugar well. This insures efficient heating and, at 

 the same time, if operated properly, it prevents the baking of the 

 milk on the heating surface. The disadvantage of this double sys- 

 tem of heating is that the overflowing kettle has to be watched very 

 closely. 



Advantages and Disadvantages of Different Methods of Heat- 

 ing. — In most factories, in' this country, the first named method is 

 used. Steam is turned direct into the milk until it boils up. This is 

 the oldest and most primitive method. While very simple in opera- 

 tion, this method has serious objections. At best, much of the 

 steam used condenses in the milk, increasing the amount of water 

 that has to be evaporated. It, therefore, prolongs the process of 

 condensing and increases the cost of manufacture. This is espe- 



Fig. 8. The hot well or forewarmer 



Courtesy of Arthur Harris & Co. 



