THE: SPRAY PROCESS 305 



pre-condensing the milk before spraying'. The spraying of un- 

 condensed milk appears to produce a more flaky powder while 

 the spraying of condensed milk results in a more granular 

 powder. The flake shape does not pack as closely together as 

 the granular shape. This is obviously an advantage in favor of 

 ore-condensing. 



However, the physical shape and condition of the powdered 

 milk can be controlled to a considerable extent by modification 

 of the coarseness or fineness of the spray. In fact, by such modi- 

 fication it is possible to make a distinctly granular product from 

 uncondensed milk, and a decidedly flaky product from the pre- 

 condensed milk. 



The finer the spray the more flaky the milk powder; the 

 coarser the spray the more granular the milk powder. The fluid 

 milk makes a finer spray than the condensed milk ; therefore the 

 more flaky condition of the powder from the former. 



Aside from the concentration of the milk to be sprayed, the 

 fineness or coarseness of the spray can be regulated by the size 

 of the orifice of the spray nozzles and by the pressure of the 

 milk. The larger the orifice or the lowier the pressure,, or both, 

 the coarser will be the spray and consequently the more granular 

 the milk powder. Therefore, in order to reduce the flakiness 

 and bulkiness of milk powder made from uncondensed milk, and 

 to make this milk powder more granular, the orifices of the 

 spray nozzles must be relatively large or the pressure of the 

 milk must be relatively low, or both. Superheating of the milk 

 (boiling it at 212 degrees F.) by turning steam direct into it 

 also assists in minimizing the fluffiness and bulkiness of the re- 

 sulting milk powder but it diminishes the solubility of the 

 product. 



Effect of Pre-condensing on Keeping Quality of Spray Milk 

 Powder. Inasmuch as the spray milk powder that is now com- 

 mercially manufactured does not contain enough moisture, 

 when properly desiccated and protected from dampness, to 

 sustain bacterial action, the keeping quality of this product does 

 not materially depend on bacterial decomposition or freedom 

 therefrom. 



Milk powder does became stale with age, however, and 

 much of it gradually develops a tallowy flavor and odor. This 



