322 COMPOSITION AND PROPERTIES OF MILK POWDERS 



point and held there for five minutes. The water lost by evapora- 

 tion was replaced. The hot solutions were then filtered and analyzed 

 for total solids. 



The results of the above tests show that the spray-process 

 powder when made from milk that was not heated above 150 de- 

 grees F. before desiccation, had the power of returning into an 

 emulsion in cold water that would filter in a similar manner and 

 would pass through the filter with a similar degree of completeness 

 as ordinary milk. The powder was substantially completely soluble. 



When made from milk that had been heated to the boiling point, 

 the spray-process powder lost slightly over 10 per cent of its solu- 

 bility. About one-half of this loss was recovered upon heating the 

 water and powder mixture to the boiling point. 



The film-process powder in cold water went into a filterable 

 emulsion to the extent of from 60 to 70 per cent of the powder 

 added, and in hot water to the extent of from 78 to 80 per cent of 

 the powder added. 



The very marked difference in solubility of the powders from 

 the two processes could be readily observed also without chemical 

 analysis. When the solutions of the film-process powders were 

 allowed to remain at rest in test tubes there would always gather 

 a very considerable deposit of solid matter in the bottom. This was 

 the case in both hot and cold water, but the deposit was very con- 

 siderably more voluminous in the cold mixture than in the hot 

 mixture. 



In the case of the spray-process powders no such deposit of 

 solid matter could be detected, neither in the hot nor in the cold 

 mixtures. , 



It is further interesting to note that the percentage of protein 

 found in the filtrates from all the powders with the exception of 

 the hot solution from the film-process cream powder, followed very 

 closely the percentage of total solids in the same filtrates. This 

 suggests very obviously that the degree to which the solubility, or 

 better the power of the milk powder to return to the character of 

 the original milk, is impaired by the process of desiccation, is largely 

 controlled by and depends on the extent to which the process of 

 desiccation changes the physical properties of the protein of milk. 



Miscibility and Readiness of Solution of Milk Powders. 

 The rapidity and readiness with which milk powders go into so- 



