The normalized extraction curves were obtained by plotting the
mass fraction of recovered essential oil (Mt/M∞) versus the
extraction time. The mass fractionwas calculated as the ratio of the EO's mass obtained at time t (Mt) to the EO's mass obtained at the end of the process (M∞).
Data were fitted to expressions described in eq. (3.5),
and the associated parameters k1 and k2 were determined by means of nonlinear regression. The obtained values of k2 were then used to calculate the mass transfer coefficient ks (eq. (3.7)).
Additionally, the time at which the phase change occurs was registered as the point in which the slope changes (tc)