Winnowing is a separation method in which heavier components of the mixture are separated from the lighter substances with the help of wind or by blowing air.
Lighter husk particles are usually separated from heavier seeds of grain by this method.
Winnowing is based on the principle of different weights of components of a mixture, and the rate of wind. When a mixture allows falling, the lighter particles are blown away by the wind and deposited away from the heavier particles.