144 Condensed Milk and Milk Powder 



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' concentrated, otherwise sugar 

 crystallization may set in. It is advisable 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 con- 

 densed milk may lie in the pan itself. Where the water used for 

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

 condenser is very close to the goose neck of the pan, as is the case 

 with most of the vacuum pans in use, the chilling of the vapors and 

 of the spray of milk rising from the pan is so sudden, that sugar 

 crystals are prone to form in the spray and along the walls of the 

 pan. These crystals either stick to the side of the pan, or fall back 

 into the milk where they later multiply and cause the milk to become 

 sugary. Trouble from this source can be avoided by either raising 

 the temperature of the water that goes to the condenser which is, 

 however, not practical under most conditions, or by closing the holes 

 in that portion of the spray pipe which is nearest the pan. This can 

 easily be done by wrapping a piece of galvanized iron or tinplate 

 around the portion of the spray pipe to be closed, or by filling the 

 holes with solder, or by replacing the old spray pipe by a new and 

 shorter one, properly constructed. 



Superheating at End of Batch. — Sometimes the manufacturer 

 is persistently troubled with the appearance of crystals in the con- 

 densed milk of monstrous size, as 'large as rice kernels; this con- 

 dition arrives usually very gradually. During the first few days 

 after manufacture, only a few of these large crystals may appear 

 in some of the cans. In the course of a few weeks, all of the cans 

 may contain specimen of these "rice crystals" which increase in 

 number until the entire contents of the cans are one mass of "rice 

 crystals," rendering the milk unsalable. The direct causes of this 

 particular kind of sugar crystallization are excessive concentration 

 of the condensed milk, the use of too much steam pressure in the 

 coils and jacket when condensation is near completion, delay in the 

 drawing off of the condensed milk from the pan, and leaky steam 

 valves in the pipes leading to jacket and coils. 



Toward the end of the condensing process the milk becomes 



