Innovative ultrasonic emulsification of cinnamon essential oil pickering emulsion stabilized by rice straw-derived...

For the first time, ultrasonic emulsification was studied for cinnamon essential oil (CEO) Pickering emulsion, stabilized by cellulose nanocrystal (CNC) from rice straw. Sonication proved to be an effective method for emulsifying CEO, creating small emulsion droplets around 700 nm in size, with an even dispersion characterized through a low polydispersity index. The biomass-derived CNC exhibits high encapsulation efficiency (> 95 %) with varying CEO concentration (5-25 vol%), creating droplets with negative surface charge with limited aggregation of emulsions. Optimization through the Box Behnken design using response surface methodology provides a model for the interaction and effects of variables towards the formulation. Optimal condition was concluded to be at 11.47 vol% CEO, 0.84 wt/vol% CNC and at 6 sonication cycles. The optimized Pickering emulsions retain the antimicrobial properties of CEO, with a large inhibition zone and low MIC value of around 0.048 vol% CEO. DPPH inhibition assay indicates that the emulsification process enhances the antioxidation properties of cinnamon essential oil, expressed through a lower IC₅₀ of 0.90 vol% CEO, in comparison to pure essential oil at 1.33 vol% CEO. Overall, this research proposes a novel approach towards using nanocellulose as carriers for essential oil with potential in a large variety of applications.