**5. Conclusions**

This study explored the optimum preparation procedure of LEO-NEs using SFEs and RSM. The optimal parameters were as follows: HLB value of 13, surfactant content of 0.157 g/mL, ultrasonic time of 23.50 min, and ultrasonic power of 761.65 W. The optimized mean droplet size was 64.60 nm. In addition, the TEM images and storage results demonstrated the good dispersion and stability of LEO-NEs. The antioxidant activity experiments showed that LEO-NEs had better antioxidant capacity than essential oils. Some of the characteristics of LEO-NEs investigated in this study and future endeavors may lay the foundation for the practical application of antioxidant activity and other biological activities of LEO-NEs.

**Author Contributions:** Conceptualization, J.G.; methodology, T.L.; software, T.L. andW.Z.; writing—review and editing, T.L., Y.S. and J.G.; visualization, T.L., W.Z. and Z.G.; supervision, G.L., F.F. and Y.S.; project administration and funding acquisition, Y.S. All authors contributed to the article and approved the submitted version. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was financially supported by the Agricultural Science and Technology Innovation Project of Hunan Province, China, (2021CX05, the Changsha Municipal Natural Science Foundation (kq2202332, kq2014070), the Agricultural Science and Technology Innovation Fund of Hunan (2020CX47), the Key Laboratory of Agro-Products Processing, Ministry of Agriculture and Rural Affairs of China (S2021KFKT-22), the National Natural Science Foundation of China (32073020), and the Hunan innovative province construction project (2019NK2041).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data is contained within the article.

**Conflicts of Interest:** The authors declare no conflict of interest.
