Star anise essential oil nano-emulsion: preparation, characterization, and performance research

Protein-stabilized star anise essential oil nano-emulsion (SAEO-NE) was successfully prepared using an ultrasound-assisted method to address the intrinsic defects and enhance the bioavailability of star anise essential oil (SAEO). In this study, the polydispersity index (PDI), particle size, and zeta potential (ZP) of SAEO-NE were used as performance indicators, and the optimal preparation conditions were determined to be an emulsifier dosage of 5%, an ultrasonic power of 270 W, and an ultrasonic time of 15 min. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analyses revealed that the resulting nanoparticle exhibited a uniform spherical shape, with a particle size of 246.5 ± 1.35 nm and a ZP of -38.97 ± 0.45 mV. Rheological analyses further confirmed the favorable rheological characteristics of the nano-emulsion. Moreover, SAEO-NE demonstrated robust adaptability across varying salinities (100, 200, 300, and 400 mM) and pH levels (1, 3, 5, 7, 9). After storage at 4 °C for 5 weeks, the nano-emulsion maintained particle sizes below 300 nm, indicating excellent storage stability. In addition, the in vitro antioxidant evaluation showed that SAEO exhibited enhanced antioxidant activity after nano-emulsification.