An apparatus for the treatment of powder, grain, paste products or the like has a treatment chamber provided with a loading mouth for at least one powder, grain or similar product and with a discharge mouth for the product; a closing cap for the discharge mouth; and at least one annular manifold, which is obtained in the discharge mouth or in the closing cap and communicates with the outside through an annular outlet channel configured to feed a compressed air flow along an inner surface of the discharge mouth and/or along an outer surface of the closing cap.