328 ComMposrrtioN AND PROPERTIES OF MirK Powpkirs 
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 which 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. 
tain conditions does, become infested with insect life, such as 
Milk powder may, and under cer- 
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 1s 
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 powder has an inherent tendeney to “lump up.” 
This is especially true of flaky powders. Phe 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 
