118 EVAPORATED MILK SEALING 



spores are very resistant and require excessively high sterilizing 

 temperatures to be destroyed. 



In the filling of the venthole cans the foaming of the evapo- 

 . rated milk frequently causes serious annoyance. This can be 

 avoided by having the milk at the proper temperature at the time 

 of filling. Experience has shown that warm milk and milk 

 excessively cold are most apt to foam profusely. Under average 

 conditions, milk at a temperature of 60 to 70 F. generates the 

 least amount of foam and at this temperature the filling is ac- 

 complished most readily. 



SEALING 



The filled cans should be capped and sealed at once. The 

 seal must be hermetical and strong enough to withstand the 

 strain of the subsequent sterilizing process. With the exception 

 of the " Sanitary can," seals without solder have so far proven 

 unsatisfactory in the canning of evaporated milk. They are 

 prone to weaken in the sterilizer and cause "leakers." Most of 

 the cans on the market containing evaporated milk are, therefore, 

 sealed with solder. Sealing evaporated milk cans with solder is 

 by far the safest method. For details of methods of sealing 

 see Chapter VII. 



For the sealing or tipping of the venthole cans an automatic 

 tipper is usually attached to the filling machine, so that when 

 the cans leave the filling machine, they have also been sealed. 



It is exceedingly important that the sealing be done per- 

 fectly, because the minutests leaks cause the evaporated milk in 

 the cans to become contaminated causing spoilage. In order to 

 detect cans with imperfect seals all the cans, as they come from 

 the filling and sealing machine, are carefully inspected for leaks. 

 This may be done by the use of a test bath consisting of a narrow 

 oblong trough, filled with hot water and through which the cans 

 pass on an endless chain. In the case of leaky cans, the heat ol 

 the hot waterbath expands the air in the cans and causes it to 

 escape through the leak in the seal and perculate upward in the 

 water in the form of air bubbles. The operator standing over 



