Kinetic model of solute aqueous extraction from Fennel (Foeniculum vulgare) treated by pulsed electric field, electrical discharges and ultrasonic irradiations

This work investigates the aqueous extraction from Fennel (Foeniculum vulgare) assisted by pulsed electric field (PEF), electrical discharges (ED) and ultrasound irradiations (UI). It aims the improvement of the solutes yield and the extraction kinetics at room temperature.Fennel gratings of size (1.5 × 0.75 × 30-50 mm³; width × height × length), were treated by PEF (intensity: 50-1200 V/cm and number of pulses: 50-1000), ED (voltage: 40 kV and number of discharges: 10-60) and ultrasound (intensity: 400 W/cm² and treatment duration: 10-350 min). The liquid-to-solid (weight/weight) ratio equal to 2. All tests were carried out at room temperature (20 °C), under stirring at 250 rpm. The extraction kinetics was modelled using a simplified two-exponential kinetic model, which corresponds to mass transfer in two stages (rapid washing and slow diffusion).The optimal parameters of PEF, ED and UI, giving the maximal juice yield, were determined and the effect of these three treatments on the mass transfer rate was studied.