318 COMPOSITION AND PROPERTIES 01- MILK POWDERS 



^Solubility of Milk Powders. -If milk powders are to take 

 the place of fresh milk or condensed milk on the table of the con- 

 sumer, and for most of the industrial uses to which they are being 

 put, they must be readily soluble. One of the greatest obstacles 

 in the progress of the milk powder industry has been that the 

 dried milk of most of the processes failed to be readily and com- 

 pletely soluble. Earlier processes prescribed the admixture to 

 the milk of alkalies in order to preserve the solubility of the pro- 

 teids, which otherwise were rendered insoluble by the high heat 

 of the respective processes. It is obvious that a dried milk, the 

 solubility of "which can be retained only by the admixture of al- 

 kalies, is a poor substitute for milk, and the very principle of add- 

 ing chemicals to a food product like milk, is contrary to our ideal 

 of successful manufacture of high quality of product. 



The term "Solubility" is here used in the broader sense of 

 the word. Milk is not a true solution. It is part solution and 

 part emulsion. "Solubility" here implies a powder, in which those 

 constituents which are in complete solution in normal fluid milk, 

 have retained their original solubility, such as the sugar of milk, 

 and in which those constituents which are present in normal fluid 

 milk in the form of an emulsion, as is the case with the casein, 

 fat and part of the ash, have retained their original emulsifying 

 power. In short, the term "solubility," as used in this discussion, 

 means those attributes of the milk powder that enable the pow- 

 der, when mixed with water, to again form a solution and emulsion 

 of a character, physically and mechanically, similar to that of nor- 

 mal fluid milk. 



The solubility of milk powders varies principally with the 

 quality of the fluid milk and with the process of manufacture. 



By quality of milk, as here referred to, is meant chiefly the 

 acidity. The combination of the heat of desiccation and of high 

 acidity, tends to rob the protein and ash constituents of the re- 

 sulting powder of their natural solubility. The higher the de- 

 gree of acid in the fluid milk, the lower 'will be the solubility of 

 the powder. The fresher and sweeter the milk at the time of desic- 

 cation, the more soluble will be the powder, other factors being the 

 same. 



For this reason many milk powder factories are endeavoring 



