A device for producing milk foam uses Couette flow and a high shear stress that is accordingly applied to a milk-air mixture between two concentrically arranged cylinders. The cylinders are rotated relatively to another. The high shear stress leads to an emulsion of the milk and the air, which is the basis for a foaming effect, once the emulsion flows out of a gap between the two cylinders and expands. The parameters of the device that mainly influence the foaming effect are the width of the gap and the relative rotation speed of the cylinders.
