SWEETENED CONDENSED Miwc HEATING 



61 



of the milk to stick to the heating surface is a permanent obstacle 

 and efforts to overcome this frequently result in sacrificing thor- 

 oughness of heating. 



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 

 heated by turning ste.am 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 prevented by 

 keeping the milk in constant motion. 

 In this case the milk is usually 

 heateji to about 170 degrees F. by 

 the jacket and from there on the 

 temperature is raised to that desired, 

 by turning steam direct into the hot 

 milk. Still others are heating the 

 milk by means of large continuous 

 pasteurizers in which case hot water 

 or steam serves as the heating medi- 

 um. 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 con- 

 tinuous pasteurizer and the plain or jacketed kettle is used. The 

 milk is heated to nearly the desired temperature in the pasteur- 

 izer. From there it flow's into the kettle, where the heating is 

 completed. This method insures efficient heating and, at the 

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

 milk on the heating surface. 



Advantages and Disadvantages of Different 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 some objections. At 



Figf. 13. 

 The hot well or forewarmer 



Courtesy of Arthur Harris & Co. 





