56 



SwHRTKNliD CoNDKNSliD MlI^K HEATING 



A variety of methods and numerous different types of machines 

 are used for this purpose in the different milk condensing factories. 

 Some use large copper kettles in which the milk is heated by turning 

 steam direct into the milk. Others use jacketed copper kettles 

 equipped with a revolving agitator. The milk is heated by turning 



steam under pressure into the jacket 

 and the burning of the milk is pre- 

 vented by keeping the milk in constant 

 motion. Still others are heating the 

 milk by means of large continuous 

 pasteurizers in which case hot water 

 or steam serves as the heating medium. 

 The milk passes in a thin layer be- 

 tween two water-heated surfaces, one 

 of which is revolving. In some fac- 

 tories the milk is forced through a 

 series of ])ipes inclosed in a hot water 

 or steam jacket. 



Finally, in some condenseries a 

 combination of the continuous pas- 

 teurizer 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 efflcient 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 system of heating is that the overflow- 

 ing kettle has to be watched very closely. 



Advantages and Disadvantages of Diiferent Methods of 

 Heating. — 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 

 operation, 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- 

 cially true where the boilers are located at some distance from the 

 hot wells and the steam pipes are not well insulated, causing the 



Fig. 11. 

 The hot well or forewarmer 



Courtesy of Arthur Harris & Co. 



