246 MANUFACTURE OF MII.K POWDER 



DEFECTS OF MILK POWDERS 



High Water Content. In order to insure keeping quality, milk 

 powders must be as free from moisture as possible. Milk powders 

 are not sterile, nor are they supposed to contain preservatives, such 

 as sucrose and chemicals. Their only safeguard against bacterial 

 fermentation and spoiling is their comparative freedom from water. 

 Unless the process fulfills this requirement, milk powders will not 

 keep and their chief virtue, which renders them most valuable, is 

 forfeited. 



Insoluble Milk Powders. If milk powders are to take the 

 place of fresh milk or condensed milk on the table of the consumer, 

 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 completely soluble. 

 Earlier processes prescribed the admixture to the milk of alkalies 

 in order to preserve the solubility of the proteids, which otherwise 

 were rendered insoluble by the high heat of the respective pro- 

 cesses. It is obvious that a dried milk, the solubility of which can 

 be retained only by the admixture of alkalies, is a poor substitute 

 for milk, and the very principle of adding chemicals to a food prod- 

 uct like milk, is contrary to our ideal of honest and successful man- 

 ufacture of high quality of product. In the most approved pro- 

 cesses now in use, the milk is never exposed to temperatures high 

 enough to render the proteids of the resulting milk powder in- 

 soluble, and in their applications the use of solvents is unnecessary. 



Non-miscible Milk Powders. The miscibility of the dried 

 milk with water depends, aside from its solubility, on the physical 

 condition of its butter fat and the casein. If the process employed 

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

 impossible to reduce the dried milk to a homogeneous fluid, similar 

 to normal fresh milk. The fat in such milk will rise to the surface 

 quickly, similar to the fat in a mixture of oil and water. 



In fresh and normal milk the casein is present, not in solution, 

 but in suspension. The particles of casein are very minute and 

 form an intimate mechanical union with the water. In this condi- 

 tion they are present in the form of a homogeneous emulsion with 

 the other ingredients of the milk. When the milk is desiccated at 

 high temperatures, the particles of casein lose their property of 



