324 COMPOSITION AND PROPERTIES OF MILK POWDERS 



than the film-process powders, hence the former should go in solu- 

 tion more rapidly than the latter. 



The above facts concerning the relation of fineness and flakiness 

 of milk powder to ease and speed of solution prevail to a certain 

 point. When that point is exceeded mechanical handicaps enter 

 into the results that tend to retard solution, at least in the beginning. 

 In the case of excessively fine and flaky milk powders, the exposed 

 surfaces are so great and the particles so small that when the powder 

 is placed into water, the rapid solution of the powder that comes 

 into immediate contact with the water causes the powder to run 

 together and paste, forming a pasty coating around the remainder 

 of the powder. This coating hinders and retards the penetration of 

 the powder by the water and thereby renders complete solution 

 slower, at least at the start. 



This difficulty is generally not experienced with the film-process 

 powders, which are of a granular nature. It can be largely avoided 

 in the case of the spray-process powders by so adjusting the orifice 

 of the spray nozzles and the pressure of the milk, as to increase the 

 coarseness of the spray. The coarser the spray the less flaky and 

 the more granular the powder. High pressure and small orifice in 

 spray nozzles produce a very fine spray and a flaky powder. Low 

 pressure and large orifice in spray nozzles produce a less fine spray 

 and a more granular powder. 



The concentration of the milk at the time of spraying also in- 

 fluences the coarseness or fineness of the spray to a considerable 

 extent. Other conditions being the same, the higher the concentra- 

 tion of the milk at the time of spraying the coarser the spray and 

 the less flaky and the more granular the resulting milk powder. 

 When the milk is sprayed before previously condensing it, a finer 

 and flakier powder is produced than when the milk is first con- 

 densed at the ratio of about 4:1, and the condensed milk is sprayed, 

 always assuming, however, that other conditions, such as orifice of 

 spray nozzle and pressure of milk be the same. It is possible, even 

 by spraying the fluid, uncondensed milk, to produce a powder that 

 is distinctly granular, by the proper adjustment of the above factors. 



The miscibility of the dried milk with water depends, aside 

 from its solubility, readiness of solution and character of the protein, 

 on the physical condition of its butter fat. If the process employed 

 is such as to destroy the globular form of the fat globules, it is 



