The conditions of the process used to prepare a nanoemulsion consisting of cinnamon essential oil and medium-chain triglycerides (MCTs) as the oil phase and modified starch (e.g., octenyl succinic acid modified starch) as the emulsifier were investigated. An orthogonal design method was adopted, where the parameters and conditions of high pressure homogenization were optimized according to emulsion particle size, and the Turbiscan dispersion stability analyzer was used to analyze the particle size and the stability of the nanoemulsion. Consequently, an oil-in-water nanoemulsion with a particle size of 90~120 nm was prepared with the following conditions: weight percentage of emulsifier, 20%; weight percentage of oil, 10%; mass ratio of cinnamon oil to MCT, 1:3; homogenization cycles, six; and homogenization pressure, 100 MPa. Moreover, the particle size was uniform, and no floatation and sedimentation occurred during storage of the nanoemulsion. Gas chromatography-mass spectrometry analysis identified 99.64% of the components from the cinnamon essential oil, and the relative contents (percentage) of all components were calculated using the peak area normalization method. The main compounds in the essential oil were cinnamaldehyde, cinnamic acid, α-pinene, 2-methoxycinnamaldehyde, α-ylangene, and α-cadinol, all of which did not change apparently throughout the process. The addition of 83% MCT to the oil phase helped to slow Ostwald ripening of the emulsion, and the retention rate of cinnamon essential oil was above 85% after 15 d of cold storage.
