Condensed Miek and Miek Powder 83 



increase the labor and difficulty of cleaning. It is best to heat the 

 milk to as near the boiling point as possible and hold it there for 

 five to ten minutes, provided that the capacity of the factory war- 

 rants this delay. In this heating the casein of the milk is somewhat 

 changed. There occurs partial, though invisible, precipitation, and 

 the higher the temperature to which the milk is heated, the more 

 pronounced is this change. This change is desirable, because the 

 casein thereby surrenders, to a limited extent, its power and ten- 

 dency to form a firm curd in the sterilizer. 



CHAPTER IX 

 CONDENSING 



The same apparatus, the vacuum pan and pump, are used for 

 condensing the milk, and the process of condensing is principally 

 the same as in the case of sweetened condensed milk. The fresh 

 milk is condensed at the ratio of two to two and one-half parts of 

 fresh milk to one part of condensed milk. In some factories it is 

 customary to superheat the milk in the pan before it is drawn off, 

 i. e., the steam to the jacket and coils is shut off, the water valve is 

 closed, the vacuum pump is stopped and "live" steam is passed into 

 the condensed milk. This is done to swell or thicken the milk and 

 partly precipitate the curd, in order to prevent the formation of too 

 hard a curd in subsequent sterilization. When the vacuum has 

 dropped to about six or eight inches and the temperature has risen 

 to 180 or 200 degrees F., the super-heating is stopped, the vacuum 

 pump is started again and the condensing completed. In other fac- 

 tories the superheating is omitted. 



STRIKING 



The striking, or sampling and testing for density, of evaporated 

 milk, is more easily accomplished than that of the sweetened con- 

 densed milk. When this product has nearly reached the proper 

 density, it is not viscous and syrupy, containing no cane sugar. It 

 resembles in consistency rich milk or thin cream and has a specific 

 gravity of 1.05 to 1.075 at 15.5 degrees C. or 60 degrees F. 



Samples. are drawn from the vacuum pan as described under 



