Development of free-flowing peppermint essential oil-loaded hollow solid lipid micro- and nanoparticles via atomization with carbon dioxide

• Essential oil-loaded hollow solid lipid micro- and nanoparticles were developed.
• Higher loading efficiency was obtained at higher initial essential oil concentration.
• Particles released the loaded essential oil over 4 weeks.
• Initial essential oil concentration dictates the release properties.
• Particle morphology was affected by essential oil release during storage.

The main objective of this study was to overcome the issues related to the volatility and strong smell that limit the efficient utilization of essential oils as “natural” antimicrobials in the food industry. Peppermint essential oil-loaded hollow solid lipid micro- and nanoparticles were successfully formed using a novel “green” method based on atomization of CO2-expanded lipid mixture. The highest essential oil loading efficiency (47.5%) was achieved at 50% initial essential oil concentration at 200 bar expansion pressure and 50 μm nozzle diameter, whereas there was no significant difference between the loading efficiencies (35%–39%) at 5%, 7%, 10%, and 20% initial essential oil concentrations (p > 0.05). Particles generated at all initial essential oil concentrations were spherical but increasing the initial essential oil concentration to 20% and 50% generated a less smooth particle surface. After 4 weeks of storage, 61.2%, 42.5%, 0.2%, and 2.0% of the loaded essential oil was released from the particles formed at 5%, 10%, 20%, and 50% initial essential oil concentrations, respectively. This innovative simple and clean process is able to form spherical hollow micro- and nanoparticles loaded with essential oil that can be used as food grade antimicrobials. These novel hollow solid lipid micro- and nanoparticles are alternatives to the solid lipid nanoparticles, and overcome the issues associated with the solid lipid nanoparticles. The dry free-flowing products make the handling and storage more convenient, and the simple and clean process makes the scaling up more feasible.

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