Effect of electro-osmotic dewatering on the quality of tofu sheet

As a new dewatering technology with high efficiency and energy saving, electro-osmotic dewatering can be applied to food processing. The objective of this work was to study the effect of combined field dewatering (CFD) involving electro-osmosis and mechanical pressure. on the quality of tofu sheet. Combined field dewatering was performed on the dewatering process of tofu sheet for 10 to 30 min at a voltage ranging from 30 to 50V under various pulse-time ratio (t(+) = 120 s, t(-) = 5 s) electric field and 0.047 MPa pressure field. The texture and structure of tofu sheet after treatments were examined by a rheometer and scanning electron microscope (SEM). The result showed that the three quality indexes, i.e., hardness, tensile strength, and ductility of tofu sheet near the anode were 45%, 30%, and 12% higher respectively than those dewatered by common mechanical pressure method. However, those near the cathode were 15%, 25%, and 10% lower respectively. When the electric field was applied for 10 min at 30V, these indexes reached their maximum values. Meanwhile, the tofu sheet structure near the anode was more compact and homogeneous than that near the cathode. The result indicated that CFD could enhance the quality of tofu sheet.