Spray drying has been found the most suitable process for removing the last
part of the water, since spray drying can convert milk concentrate into a
powder while still keeping the valuable properties of the milk.
The
principle of all spray dryers is to transform the concentrate into many small
droplets which are then exposed to a fast current of hot air. Because of the
very large surface area of the droplets (1 1 of concentrate will be atomized to
1.5 x 1010 particles of 50µ with a total surface of 120 m2) the water
evaporates almost instantaneously and the droplets are transformed into powder
particles.