Supercritical CO2 extraction of pinocembrin from Lippia origanoides distillation residues. 2. Mathematical modeling of mass transfer kinetics as a function of substrate pretreatment

Abstract

Lippia origanoides and L. graveolens are natural sources of essential oils and compounds with bioactivity (e.g., flavonoids). The objective of this work was to model the extraction of L. graveolens and carvacrol-, thymol-, and phellandrene-rich chemotypes of L. origanoides using ethanol-modified supercritical CO2 as the solvent using the Broken-and-Intact Cells (BIC) and Shrinking Core (SC) models. We studied the effects of the substrate and its pretreatment (grinding versus pelletization) and extraction conditions on extraction rate and yield. Model parameters for the BIC (fraction of broken cells, partition coefficient, and microstructural factor) and SC (micro structural factor) models were best-fitted to experimental cumulative extraction curves. Pelletizing favored rupture of inner cells, but made part of the oleoresin unavailable for extraction, partially due to thermal damage. SC was appropriate only for pelletized substrate, because it hypothesizes an interconnected porous space filled with condensed oleoresin, whereas that BIC was much better for the extraction of ground substrates.