324 



MILK AND ITS HYGIENIC RELATIONS 



' 4. The separator. The separated milk may be dried separately, 

 in which case the cream is removed. When dried whole milk is wanted 

 the separated milk and cream are brought together again in a common 

 channel which carries the milk to 



' 5. A pasteurising apparatus where the temperature of the fluid is 

 raised from 70 C. to 75 C. When separated milk is treated the tem- 

 perature is raised slightly above 75 C. 



' 6. The pasteurised milk is collected in a large vacuum pan, where 

 it is heated by steam to a temperature of about 58 C. and is reduced 

 to a little less than one-half of its original bulk. When the milk has 

 reached a suitable consistency its temperature is rapidly raised to 95 C., 

 and as soon as this point is reached the temperature is brought down 

 again to 58 C. 



' 7. According tothe amount of milk in the vacuum pan the condens- 

 ng process occupies from two to two and a half hours. 



Figure illustrating the 2nd method of desiccation. 



' 8. The condensed milk is drawn into metal cylinders from which 

 it is immediately pumped into 



' 9. A small tank, from which the fluid passes into 



' 10. A powerful pump, which forces it under a pressure of 2000 

 to 3000 Ibs. through the 



'ii. Spraying apparatus, by which a cone of finely sprayed milk is 

 produced. This takes place in the middle of an opening to which a 

 current of dry air heated to 115 C. is brought by 



' 12. A large pipe. Both the hot air and the spray are projected into 



' 13. A tin-lined chamber, the internal temperature of which is 76- 

 81 C. The droplets of milk dry as they fall to the floor, upon which 

 they rapidly form a layer of granules of dry milk. 



' The current of hot air passes out of this first room into a second 

 room, where the particles which have not fallen in the first room are 

 collected. 



' When the desired amount of milk has been dried, the drying-room 



