Optimization of operating conditions of Tunisian myrtle (Myrtus communis L.) essential oil extraction by a hydrodistillation process using a 24 complete factorial design

A 24 complete factorial design has been used to study the technological parameters that are responsible for the hydrodistillation process. After an appropriate choice of four critical variables, 16 experiments led to a mathematical model as a first degree polynomial presenting the response function (yield) in relation to the operating parameters. From the retained model, we were able to calculate the average response, the different effects and their interactions. The results showed that processing time, condensation flow and mass ratio plant material:water had significant effects (in absolute values) on myrtle essential oil yield (0.0350, −0.0421 and −0.0416, respectively), whereas granulometry presented a negligible effect (about −0.0084). The average essential oil yield extracted from 100 g myrtle leaves is 0.635%. Our study proved that experimental design methodology could efficiently be applied to characterize the analytical parameters affecting the hydrodistillation process and that it is an economical way of obtaining the maximum amount of information in a short period of time and with the smallest number of experiments.