Formulation of lavandin essential oil with biopolymers by PGSS for application as biocide in ecological agriculture

Essential oils, and in particular lavandin (lavandula hybrida) essential oil, can be used as natural biocides as an alternative to synthetic chemical biocides. For this purpose, agrochemical formulations of the essential oils should be physically stable in the long term and should enhance the biological performance of the agrochemical. In this work, such a formulation of lavandin essential oil obtained by encapsulation of the oil in a biodegradable polymer has been studied. Two high-pressure precipitation techniques, particles from gas saturated solutions (PGSS) and PGSS-drying, have been applied to perform the encapsulation. The PGSS process has been used to encapsulate the oil in polyethylene glycol (PEG). With PGSS-drying the oil has been encapsulated in n-octenyl succinic (OSA)-modified starches, by removing the water form an oil-in-water emulsion stabilized using the OSA-starches as surfactants. Operating conditions were selected in order to reduce oil losses due to its dissolution in supercritical CO2 or due to emulsion destabilization. A comparison between the characteristics of the particles obtained by encapsulation in PEG with PGSS and by encapsulation in OSA-starches with PGSS-drying was done. Results revealed that encapsulation efficiencies of lavandin oil were higher in PEG microcapsules obtained by PGSS (14–66% of initial oil encapsulated). Particles show a spherical morphology and a narrow particle size distribution, which is favourable for a controlled release of lavandin essential oil.