Kinetic model of sugar diffusion from sugar beet tissue treated by pulsed electric field

Extraction of sugar from sugar beet slices was studied following various pulsed electric field (PEF) treatments (intensities from 300 to 800 V cm(-1) and number of pulses varying between 50 and 1000). Slices treated by PEF were immersed in water at ambient temperature at a liquid/solid ratio of 3. A significant increase in extraction yield was observed. This enhancement was due to permeabilisation of the cellular membrane and to the additional quantity of juice appearing on the surface of slices after PEF treatment being extracted rapidly by convection. The optimal conditions of PEF treatment were an intensity of 670 V cm(-1) and 250 pulses. The extraction kinetics was studied on the basis of two approaches: Fick's diffusion equation and a two-exponential kinetic model. The coefficient of diffusion was only slightly influenced by the conditions of PEF treatment. The two-exponential model successfully described both the rapid and prolonged stages of extraction. By heating the solution at mild temperatures of 30-50degreesC, the coefficient of diffusion was increased and the kinetics of extraction was enhanced. The quality of cellular juice obtained after PEF treatment was higher than that of juice obtained after thermal pretreatment at 75degreesC. (C) 2004 Society of Chemical Industry.