224 SWEETENED CONDENSED MILK DEFECTS 



24 to 28 per cent water. Sucrose dissolves in one half its weight 

 of water. The sweetened condensed milk does not, therefore, 

 contain a saturated solution of sucrose. 



Incomplete Solution of Sucrose. If the finished product is 

 to be smooth and free from sandiness, it is essential that the 

 sucrose which is added to the hot, fresh milk be thoroughly dis- 

 solved before the mixture reaches the vacuum pan. Undissolved 

 sugar crystals in a medium as highly concentrated as sweetened 

 condensed milk have much the same effect in a physical way, as 

 have bacteria in fresh milk in a biological way ; they multiply 

 rapidly. Therefore, if all the sugar added to the fluid milk is 

 not completely dissolved, the undissolved sugar crystals give 

 rise to wholesale precipitation of the milk sugar in this product 

 after manufacture, and since the crystals of undissolved cane sugar 

 are relatively large, their presence also gives rise to the formation 

 of milk sugar crystals of large size. Hence the sandy condition of 

 the condensed milk. Complete solution of the cane sugar can 

 best be accomplished by heating the liquid, milk or water, in 

 which the sugar is to be dissolved, to the boiling point and by 

 boiling the mixture for several minutes ; or by placing the sugar 

 on a large wire mesh strainer (about eighty meshes to the inch) 

 which stretches across the sugar well and allowing hot milk to 

 run over this sugar in{o the well below. In this way the sugar 

 crystals must dissolve before they can reach the sugar well. 



One of the safest methods of insuring complete solution of 

 the cane sugar is to dissolve it in a separate kettle in a sufficient 

 quantity of boiling water (preferably distilled water) and boil- 

 ing the syrup for five to fifteen minutes. If the syrup thus made 

 is given a few minutes rest it should become perfectly clear; 

 by its clearness, the purity of the sugar can also be observed. 

 If a scum forms at the top it should be removed ; then the hot 

 sugar syrup is drawn into the pan. Care should be taken that 

 the milk already condensing in the pan has not become too con- 

 centrated, otherwise sugar crystallization may set in. It is ad- 

 visable to inject the sugar syrup gradually, rather than to wait 

 until nearly all the milk is in the pan. 



Excessive Chilling in the Pan. The cause of grittiness of 

 condensed milk may lie in the pan itself. Where the water used 

 for condensing is very cold, and where one end of the spray 



