226 SWEETENED CONDENSED MILK DEFECTS 



because the finished condensed milk is retained in the pan as 

 the result of an accident, in all of these cases there is danger 

 of superheating, and therefore, of the production of these large 

 crystals. This danger is especially great, where the .valves of 

 the steam pipes leading to the jacket and coils are leaking, as 

 is often the case. The avoidance of excessive concentration and 

 the removal of any conditions that tend to expose the finished 

 or the nearly finished condensed milk to excessive heat will 

 usually prevent further trouble of this sort. 



Experimental results by C. S. Hudson, 1 on the solubility 

 and crystallization of milk sugar also show that milk sugar 

 crystals of large size were obtained by evaporation of a solution 

 of milk sugar at 95 degrees C. (203 degrees F.). 



Excessive Concentration. In as much as the initial cause 

 of the precipitation of a portion of the milk sugar which leads to 

 the production .of sandy condensed milk lies in the fact that the 

 milk sugar is present in this product in the form of a super- 

 saturated solution, it is obvious that the danger of sugar crystal- 

 lization and sandiness in this product increases with the increase 

 in concentration. This is fully borne out by practical experience. 

 The higher the ratio of concentration the more difficult it be- 

 comes to manufacture a smooth condensed milk. The danger 

 here is further augmented by the fact that in the very highly 

 concentrated product the tendency of superheating is augmented. 

 And the superheating gives rise to very large crystals wihich 

 render the product exceedingly coarse. The superheating is 

 due to the increased sluggishness of the very thick -condensed 

 milk in the pan, it ceases to boil vigorously enough and is there- 

 fore excessively exposed to the hot coils. It is further due to 

 the slowness with which this product leaves the hot pan. 



Improper Cooling. The method used for cooling the sweet- 

 ened condensed milk after it leaves the vacuum pan is another 

 important factor determining the smoothness or grittiness of the 

 finished product. The chief principles involved here are the 

 rapidity and extent of cooling and the amount of agitation to 

 which the condensed milk is subjected. 



In order to fully appreciate the importance of strict atten- 



1 Hudson, The Hydration of Milk Sugar in Solution, Jour. Am. Chem. 

 Soc., Vol. XXVI, No. 9, 1904. 



