470 MANUAL OF MILK PRODUCTS 



of the powdered milk the drying process is carried much farther 

 than with condensed milk. The finished product contains all 

 the solids in the original milk, but so small an amount of mois- 

 ture that bacteria and other microorganisms are unable to 

 grow. It is therefore not necessary to use additional sugar or to 

 sterilize the finished product by heat. Powdered milk contains 

 not more than three to five per cent' of moisture, and bacteria 

 which may be present in it are unable to grow, hence cannot 

 injure the product. 



The making of powdered milk is of much more recent devel- 

 opment than that of condensed milk, since this branch of the 

 dairy industry has all developed during the last twelve or 

 fifteen years. 



PROCESS FOR MAKING POWDERED MILK 



Several methods are in use for making powdered milk. 

 "One 1 is the 'Just' process which was invented by John A. 

 Just of Syracuse, New York. The milk is dried on steam- 

 heated cylinders which as they revolve are given a coating of 

 liquid milk. The heat conducted from the inside evaporates 

 the water and leaves the solids in a dry layer on the surface, 

 from which they are scraped off with knives which extend the 

 full length of each cylinder. The strong point of this process 

 is its cheapness. 



"The rights for this process were sold to a man by the name 

 of 'Hatmaker' for operations in Europe. On that account 

 this process is known in Europe as the 'Hatmaker' process. 

 By this method the milk is subjected to very high heat which 

 affects its solubility. " 



Another method is that known as the "Campbell" process. 

 By this system of drying warm air is blown through the milk 

 until it becomes very thick. It is then exposed to hot air and 



1 Data by R. S. Fleming. 



