Pulsed electric field treatment for solid-liquid extraction of red beetroot pigment: mathematical modelling of mass transfer

The extraction of red pigment and conductive matters from individual red beet tissue slices following pulsed electric field pretreatment of different durations was compared with a two dimensional bimodal Fickian diffusion model. The process appeared to be governed by two apparent diffusion coefficients, one slow and one fast. The values of these coefficients were independent of the duration of treatment, but the yield associated with each coefficient varied. Following the treatment of longest duration and treatment by freezing and thawing of the tissue, the yield from the faster diffusion coefficient accounted completely for the mass transport. The faster apparent diffusion coefficient was 2-5 times smaller than the diffusion coefficients in dilute solution. (C) 2003 Elsevier Ltd. All rights reserved.