Effect of moderate electric fields on salt diffusion into vegetable tissue

Although salt infusion, through blanching or marinating, has been known to successfully increase the electrical conductivity of solid food components, pretreatment times are long, and in most cases, equilibration between the solid and the liquid is still incomplete. A faster pretreatment method is needed. Previous studies have shown mass transfer enhancement during electrical treatment. We determined the effective diffusion coefficients, D-seff, of salt into vegetable (celery, mushroom, and water chestnut) tissue under electric field at three temperatures (25, 50, and 80 degrees C) and four electric field strengths (0, 658, 1316, and 1842 V/m). The value of D-seff was significantly (p < 0.05) increased with temperature and electric field strength for all materials (celery, mushroom, and water chestnut). Activation energies for diffusivity decreased with increasing electric field strength for celery and mushroom, suggesting a diminished role for temperature when field strength was high. No trend was found for water chestnut, implying that it was temperature insensitive. Although in an alternating field the electrophoretic driving force either aligns with or opposes diffusion during each half cycle, the net result is an increase in ion transport over time. This is consistent with the rectification theory as expressed by the Nernst-Planck equation. (C) 2012 Elsevier Ltd. All rights reserved.