Comparative study of the design of continuous aeration equipment for the production of food foams

The performances of two designs of mixing heads dedicated to food aeration are compared in terms of overrun, bubble size and energy consumption in laminar flow conditions. The first design (RS) is a standard rotor–stator combination, while the second is a multi-impeller stirred column (CF) equipped with flat-blade radial turbine impellers. Experimental data demonstrate that higher overrun can be achieved at lower rotation speed, residence time and energy consumption with RS for Newtonian media, but at the expense of larger bubble sizes than with CF. Conversely, CF is more efficient for achieving high overrun and smaller bubbles when highly shear-thinning media are involved, although energy consumption remains higher. However, for both designs, the average bubble size has been related to an invariant dimensionless parameter, the laminar Weber number. Finally, the key role of the local distribution of shear has been highlighted, even at identical average shear rate in both devices.