306 Tuk Spray Process 
must be attributed to chemical changes, one of the chief of which 
is oxidation. While there are numerous agents, which come in 
contact with, or enter into, the composition of milk powder, that 
may bring about, or may invite oxidation, air is one of the most 
likely factors to play an important role. 
Air, as is well known, acts as an oxidizing agent. Since 
there is a noticeable tendency of the product from uncondensed 
milk to be flakier and bulkier than the product from condensed 
milk, it appears that with this increased bulkiness, there may 
be more air in a given bulk, varying somewhat with the method 
of packing. 
But experience has shown that there is enough air contained 
both, in a package of milk powder made from uncondensed milk 
and in a like package of milk powder made from condensed 
milk, to cause deterioration, when other conditions, such as 
light, or temperature, or both, are favorable, or when there is 
present in the product enough moisture. 
There are no experimental results available that show any 
difference in the keeping quality of the two products and the 
experience of the commercial manufacturer points to the con- 
clusion that the milk powder made from uncondensed milk 
keeps as well as the product made from pre-condensed milk. 
Effect of Pre-condensing on Solubility of the Spray Milk 
Powder.—The flaky and fluffy powder of the uncondensed milk 
goes into solution at the start somewhat slower than the more 
granular powder made of condensed milk. ‘This is due to the 
fact that the flaky particles with their relatively large exposed 
surfaces, coming in immediate contact with the water, dissolve 
and take up water so rapidly, that they run together and paste, 
forming a coating around the remaining mass of the product, 
which renders the penetration of the water into the mass some- 
what slower at the start. [lowever, this is no indication that 
the flaky powder is less soluble than the granular powder, in 
fact the flaky powder, because of the large relative surfaces of 
its particles and, therefore, the greater area of contact, does 
dissolve more rapidly when it actually comes in contact with 
water, 
Experiments conducted by Hunziker indicate that the differ- 
ence in speed of solution between the two products is very slight 
