Ohmic heating extraction of radish (Raphanus sativus L.) leaf phenolic extract: Numerical optimization and kinetic modelling

This research aimed to model the kinetic of ohmic heating extraction method of radish (Raphanus sativus L.) leaf extract in order to understand and optimize the extraction process .The effect of extraction parameters on extraction yield, total phenol content and DPPH scavenging activity was discussed, at a gradient voltage of 10-30 V/cm, temperature of 30-60°C, solvent ration (Ethanol to water) of 30-100% and extraction time of 10-30 min. Different empirical models such as first order, adsorption and sigmoid models presented to predict the kinetics of mass transfer without taking into account the underlying phenomena. Results indicated that the effect of gradient voltage, extraction time and solvent ratio (ethanol to water) on the extraction yield, total phenolic content and DPPH scavenging activity were significant (p˂0.05). Although increasing extraction temperature significantly resulted in a lower total phenolic content and DPPH scavenging activity of extract (p<0.05), however, this parameter no significant effect the extraction yield (p>0.05). Under optimum conditions, the experimental extraction yield and total phenol content were close to the predicted values calculated from the quadratic response surface model. Based on kinetics modeling that has been done, it can be said that the sigmoid kinetic model more can represent well the experimental results of radish leaf extract by the ohmic heating method when compared with the first-order and adsorption kinetic models.