CONDENSED AND EVAPORATED MILK 259 



shown that, in some localities and at certain seasons of 

 the year, a marketable evaporated milk cannot be made 

 when the product is condensed sufficiently to contain over 

 24 per cent solids." 



When the milk is drawn from the condensing pan it is 

 ready to be canned, but as this requires some time, the 

 milk is first cooled to prevent acid development and other 

 fermentations. The cooling is usually accomplished by 

 means of a coil in a manner similar to that of cooling fresh 

 milk in a city milk plant. The cooled milk is stored in 

 sanitary tanks, drawn out a little at a time, and run into 

 the can fillers, which are operated in a manner similar to 

 the operation of the common milk-bottle filler. The can- 

 ning process is completed with the soldering on of the 

 tops. 



Sterilization. This canned evaporated milk quickly 

 undergoes fermentation unless absolutely sterilized. In 

 order to effect sterilization it is necessary to heat the milk 

 under steam pressure. The sterilizers used are similar in 

 construction and principle to the autoclave used in the 

 bacteriology laboratory, except that they are larger. They 

 are so arranged that trucks loaded with cases of milk may 

 be run into them on a track. 



The degree of heat employed and the duration of the 

 heat exposure of the condensed milk are very important 

 factors. Even perfectly sweet, normal milk curdles at a 

 temperature of 269 F., and the more concentrated the 

 milk the lower the temperature required to curdle it. 

 There are other factors, such as the per cent of casein 

 present, the relative amounts of the different ash con- 

 stituents, etc., which influence, to a greater or less degree, 

 the curdling point of milk. Temperatures ranging from 

 226 to 245 F. are used to sterilize condensed milk. 



