The total fat in the whole milk powder is a question of standardizing the raw milk prior to the processing and has got nothing to do with the drying process.
The standardizing is carried out either by adding skim milk or cream to the milk, or removing cream from the milk, depending on the content of fat in the raw milk and the fat content aimed at in the final powder. Standardizing tanks equipped with agitators are in most cases used, but other methods are also recommendable.

As the fat content in the raw milk in practically all cases is too high when producing whole milk powder, skim milk powder is sometimes used for standardizing. The equipment needed is an in-line powder/liquid blender known from recombining plants. As the solids content will increase by adding skim milk powder, the evaporator should be designed accordingly.

For an accurate determination of the fat in whole milk powder the Rose-Gottlieb method is used and for a quick determination the Gerber method is used.