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.