60 SWEETENED CONDUNSSD MII,K HEATING 



Solution of Sucrose. It is very essential that all the cane, 

 sugar which is added to the milk be completely dissolved, jn 

 order to lessen the tendency of the sugar to form large crystals 

 in the finished product. Undissolved sugar crystals in condensed 

 milk act in a physical way much as bacteria in fluid milk do in a 

 bacteriological way. They multiply rapidly, and such condensed 

 milk usually precipitates its sugar before the product reaches 

 the market. The presence of excessively large sugar crystals 

 makes the product gritty and causes the formation of a sediment 

 in the bottom of the cans; this is objectionable to the consumers. 

 When the milk is heated to the proper temperature before con- 

 densing, the. solution of the cane sugar is facilitated and the 

 tendency toward grittiness is minimized. 



Prevention of Burning Milk on Heating Surface. If cold 

 milk comes in contact with a steam-heated surface and is not agi- 

 tated vigorously, it bakes or burns onto this heating surface. The 

 milk in the vacuum pan is heated or kept hot by means of the 

 steam jacket and coils. These radiators are charged with steam 

 under pressure and consequently give off a high degree of heat. 

 If cold milk is drawn into the vacuum pan, the milk remains 

 calm for a considerable length of time. During this time it is 

 bound to bake or burn on the heating surface, giving the product 

 a burnt flavor, causing it to contain brown specks and retarding 

 the process of evaporation. If the milk is hot when it enters the 

 pan, the reduced pressure in the pan causes it to boil violently at 

 once, avoiding all danger of sticking to and burning on the heat- 

 ing surface and making possible maximum rapidity of evapora- 

 tion. 



Temperature. In most factories the milk is heated to from 

 180 degrees F. to 200 degrees F. This temperature is sufficient 

 to accomplish the three purposes. Heating the milk to the 

 boiling point tends to give it a rather pronounced cooked flavor, 

 which is objectionable. However, in the case of danger of con- 

 tamination of the milk with resistant types of undesirable bac- 

 teria, it may become necessary to practice boiling the milk. 



Manner of Heating. Thorough, efficient and rapid heating 

 of large volumes of milk to temperatures near the boiling point 

 is a problem that requires careful consideration. The tendency 



