Supercritical impregnation of lavandin (Lavandula hybrida) essential oil in modified starch

Lavandin (Lavandula hybrida) essential oil contains components with biocide properties that can be used as substitutes of synthetic drugs in livestock. This application requires an appropriate formulation of the essential oil. In this work, supercritical impregnation of lavandin oil has been proposed as a possible formulation process, due to the high solubility of lavandin essential oil in supercritical carbon dioxide. The polymer used in this work as carrier material was starch modified with the n-octenil succinate (OSA) group, in the form of powder with a particle size of 30 μm. The effects of operational pressure (10–12 MPa), temperature (313–323 K) and lavandin oil to starch mass ratio (0.2–1) were studied. Impregnation loads ranging from 25 to 150 mg lavandin oil/g OSA-starch were obtained. The distribution coefficient of essential oil between the starch and the supercritical phase as well as the essential oil load depended on the density of CO2.

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► Lavandin essential oil was impregnated in modified starch using scCO2 as impregnation solvent.
► The best results both in terms of essential oil load and partition coefficient were obtained with conditions that weakened the interactions between CO2 and essential oil (i.e., with lower CO2 densities).
► The efficiency of impregnation, defined as the fraction of lavandin oil feed to the system that is impregnated in particles, is lower than the efficiency obtained by other supercritical fluids processes (PGSS and PGSS-drying).