Nano-Emulsification Potentiates Tea Tree Oil Bioactivity: High-Stability Formulation for Dual Antimicrobial and Antioxidant Food Preservation

Essential oils play important roles in the modern food industry as additives and spices. At the same time, most essential oils have broad-spectrum bacteriostatic properties and can be used as natural antimicrobial materials. However, the application of essential oils is limited due to their strong volatility and insolubility in aqueous substrates. In this study, we used ultrasonic emulsification, carboxymethyl chitosan, and Tween 80 to formulate tea tree essential oil (TTO) nanoemulsions with high stability. With a minimum diameter of about 51 nm (PDI = 0.236 ± 0.021) post-emulsification, the TTO nanoemulsions disperse effectively in the drainage system and exhibit good stability after 14 days of storage. In addition, the bioactivity (antibacterial and antioxidant) of TTO nanoemulsions was significantly enhanced following emulsification, as evidenced by MIC and DPPH assays, indicating that nano-emulsification is beneficial to the development of various essential oils. TTO nanoemulsions can be used as a new food preservative to control the growth of bacteria and prevent the deterioration of food via oxidation.