Improvement in the Stability of Perilla Seed Oil Microemulsion and Its Role in Fat Accumulation Reduction in Caenorhabditis elegans

Perilla seed oil (PSO) possesses various physiological functions, such as lowering blood lipids and preventing cancer; however, its poor water solubility, dispersibility, and oxidative stability severely limit its application scope. Epigallocatechin gallate (EGCG) is a natural antioxidant abundant in tea leaves. In this study, PSO–casein–EGCG microemulsions were prepared, and their stability and lipid-lowering effects were evaluated. The results showed that the PSO microemulsion had a particle size of 361.23 ± 14.85 nm, a zeta potential of −20.77 ± 0.68 mV, a polydispersity index (PDI) of 0.17 ± 0.07, and an encapsulation efficiency of 94.3%. PSO microemulsions remained stable at room temperature for 5 days without droplet aggregation. The stability of the microemulsions was good when the NaCl concentration was between 0.1 and 1 mM and the pH was between 5 and 9. PSO microemulsions enhanced the oxidative stability of PSO. Additionally, PSO microemulsions significantly reduced triglyceride levels in Caenorhabditis elegans (77.50%, p < 0.005). Finally, it was found that the average lipid droplet size of ZXW618 mutant nematodes decreased by 41.23% after PSO microemulsion treatment. Therefore, PSO microemulsions may reduce fat accumulation in C. elegans by decreasing lipid droplet size. This provides new insights for advancing the application of PSO in the food processing industry.