MANUFACTURE OF MILK POWDER 



279 



spread on trays or other similar containers, and dried to a hard 

 substance in vacuum chambers or in other vaults or drying ap- 

 paratus, provided with heating devices or currents of hot air. 

 The dried product is subsequently ground to a fine powder. 

 Examples of this type of milk-drying processes are the Wimmer 

 process, the Campbell process and others. 



The Wimmer Process. The milk 

 is boiled in a vacuum pan similar to 

 that used. in the manufacture of con- 

 densed milk. The vacuum pan has a 

 deep steam jacket for heating, but in 

 the place of the usual coils, the pan is 

 equipped with a mechanical stirrer. 

 The milk is condensed at a relatively 

 low temperature and the stirrer re- 

 volves until the water content of the 

 milk is reduced to about 30 per cent 

 and the milk has become porous and 

 crumbly, though it still forms a com- 

 pact mass. The drying is then com- 

 pleted in the open air and without addi- 

 tional heating. The product is then 

 ground to a powder. This is the pro- 



cess invented b y Ole Bul1 Wimmer of 

 Copenhagen, Denmark. 



The Campbell Process. This process was invented, pat- 

 ented and improved by J. H. Campbell of New York City, U. S. 

 patent Nos. 668,159 and 668,161, February 19, 1901 ; U. S. patent 

 No. 718,191, January 13, 1903; U. S. patent No. 762,277, June 

 14, 1904; and by J. H. and H. C. Campbell, U. S. patent No. 

 668,162, February 19, 1901; and by C. H. and P. T. Campbell, 

 U. vS. patent No. 771,609, October 4, 1904. 



The Campbell process consists essentially of concentrating 

 milk to a high degree of concentration by blowing heated air 

 through it in an open vat. The milk is reduced to a very thick 

 consistency, resembling a batter. The concentrated milk is then 

 removed from the evaporating tank, is reduced mechanically to 

 small units by means of a pugging or shredding machine, or 



Fifir ' 



