Effect of electrohydrodynamic (EHD) technique on drying process and appearance of okara cake

The changes in the drying process and the appearance of an okara cake dried with an electrohydrodynamic (EHD) technique were investigated in an oven at 105 °C. During drying, the voltage was kept constant, the number of the needles in the point electrodes were 1 and 3 and the electrode gap were 35, 50 and 65 mm. The results showed that the drying time under the high electric field (HEF) condition reduced by 15–40% compared to the control at the final moisture content of 10% wb. Comparing with the drying rate at the same drying time in the different HEF conditions, the initial drying rate were found 1.7–3.2 times higher than that of the control. In addition, the electric field also had an influence on the appearance of the okara cake. The okara cake after drying kept a whole shape and there was no cranny in the surface when the HEF was supplied to, but there were some crannies and cracks in the surface of the control. However, the color of the sample exposed to the HEF became distinctly browner than that of the control, especially the part just under the needle electrode.