Chemical composition, antimicrobial activities, and microencapsulation by complex coacervation of tea tree essential oils

The chemical composition and antibacterial activities of five tea tree essential oils are analyzed. GC–MS analysis reveals that 1,8-cineole, terpinen-4-ol, p-cymene, α-terpineol, and α-pinene are the representative composition. By comparison of the diameter of inhibition zone, oil of Melaleuca leucadendron Linn. (TTO1) shows the best antimicroorganism effects on Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Subsequently, the coacervation between gelatin (GE) and gum Arabic (GA) for microencapsulation as functions of pH, GE–GA ratio, emulsifiers, homogenization speed and time, and microfluidization are investigated. The optimum parameters for the coacervation effectiveness of TTO1 and emulsifier S20 are emulsification at 10,000 rpm for 1 min, the ratio of GE–GA as 1:2 with a concentration of 1%, and pH of 4.0. The microcapsules have a particle size of 52.601 μm, spherical multinuclear morphology, and strong physical stability which show potential for their application in the controlled release of reactive materials and anticorrosion of cosmetics and foods. Novelty impact statement The tea tree essential oils showed different antimicrobial potential toward the bacterial species tested. After microfluidization, tea tree essential oil microcapsules prepared by a complex coacervation method generated smaller particles with greater encapsulation efficiency. The microcapsules synthesized in this study can be utilized as a novel preservative in the food industry or used for the encapsulation of other bioactive compounds.