Effect of increased gravitational acceleration in potato deep-fat frying

- Existence of a wide evaporation zone instead of a sharp evaporation front.
- Heat transfer depends on gravity term in non-linearly way.
- Frying intensification can achieved by increasing gearth up to about 3 · gearth.

This work extends our previous studies on crust thickness evolution and evaporation front propagation during deep fat frying of potato sticks (French fries) by incorporating the effect of increased gravitational acceleration. Scaling of gravitational acceleration allows scaling of buoyancy forces which control the heat transfer from hot oil to potato surface. For this, a special device is constructed which permits (a) temperature recording at specified positions below the potato surface (i.e. 0.5, 1.0 and 1.5 mm), (b) exposure of only one surface of a potato stick to hot oil, (c) rotation of the exposed surface at orientations 0° (horizontal, top), 90° (vertical, side) and 180° (horizontal, bottom), and (d) execution of deep fat frying experiments at increased gravity levels (i.e. 1.8, 3.0, 6.0 and 9.0 · gearth). The latter is achieved by means of a large diameter centrifuge (European Space Agency). Temperature recordings and crust thickness evolution indicate that heat transfer during frying depends on gravity level but differently at different potato orientations. Most significant variations with gravity are found up to 3.0 · gearth and for 0° orientation. Moreover, crust thickness evolution diverges from the evaporation front propagation in all times supporting the notion of a wide evaporation zone rather than a sharp evaporation front.