328 COMPOSITION AND PROPERTIES OF MILK POWDERS 



To what extent the brass nozzles jeopardize the keeping- 

 quality of the powder is difficult to say. But it is well known 

 that they suffer considerable wear as the result of the spraying, 

 and this means that the atomized spray carries off particles of 

 brass w ! hich later become a part of the finished powder. 



The metal drums used in the film-drying- process are gen- 

 erally constructed of metal other than copper. Many are of 

 highly polished steel and some are nickel plated. The desiccat- 

 ing equipment used in this process is therefore not exposing the 

 product to copper and copper salts, thereby largely avoiding the 

 possibility of injuring the keeping quality of the resulting milk 

 powder through this channel. 



Insects in Milk Powder. Milk powder may, andninder cer- 

 tain conditions does, become infested with insect life, such as 

 maggots, weevil, etc. This infection may take place in the fac- 

 tory itself, but more often it is the result of contamination after it 

 leaves the factory. 



Such contamination is generally due to a faulty package. 

 Whenever the seal is broken the danger of insect invasion is 

 very great. Manufacturers have found also that packages sent 

 to the tropics are especially prone to succumb to this nuisance, 

 the prevention of which necessitated the packing of the powder 

 destined for the tropics, in hermetically sealed cans. 



Lumpy Milk Powder. As previously stated, milk powder 

 exposed to dampness invariably becomes lumpy, and even when 

 exposed to atmospheric air of normal humidity it will gradually 

 form lumps, owing to the highly hygroscopic properties of the 

 milk powder. In order to prevent lumpiness, the powder must 

 be stored in a dry place and packed in a manner to protect it 

 against direct contact with atmospheric air. 



At best milk pow,der has an inherent tendency to "lump up." 

 This is especially true of flaky powders. The more granular 

 powders yield less readily to this defect. 



In order to minimize the tendency toward lumpiness, the 

 milk powder should be allowed to cool, after desiccation and 

 before sifting and packing. If sifted and packed while still 

 warm, the soft condition of the fat causes the particles to lump 

 together after sifting. If sifted and packed after the milk powder 

 has surrendered its heat, the fat has had an opportunity to 



