Characteristics and antimicrobial activity of microfluidized clove essential oil nanoemulsion optimized using response surface methodology

Abstract Clove essential oil nanoemulsion with optimal antimicrobial activity and stability was formulated and analyzed using response surface methodology with a central composite design (CCD). The optimal clove oil nanoemulsion was obtained from a microfluidizer (10,000 psi of operating pressure) of 1% (v/v) clove oil and 3% (v/v) of Tween® 80 (surfactant), with a droplet size of 30.76 nm, 0.179 polydispersity index (PDI), −50.01 mV Zeta potential, and 7.81 cP viscosity. It also exhibited good stability against particle aggregation and phase separation during 48 h of storage at 5°C. Clove essential oil nanoemulsion had higher amount of eugenol, but lower amount of benzyl alcohol and caryophyllene than those contained in bulk oil. The clove oil nanoemulsion exhibited better antimicrobial activity against Staphylococcus aureus , Escherichia coli , and Pseudomonas aeruginosa when compared to clove oil. Bacterial cell morphological destruction caused by clove oil nanoemulsion or clove oil was also observed using a scanning electron microscope and energy dispersive x‐ray spectrometer (SEM‐EDS). The results suggested that the fabrication of clove essential oil into nanoemulsion improved its antimicrobial activity and has the potential to be used as a natural preservative for food applications. Novelty Impact Statement The experiments in this research were designed to determine the feasibility of using the clove oil nanoemulsion as antimicrobial agent directly in food and its stability if used under different food processing conditions, storage, or usages. Our study is, however, not only the first to optimize the important factors required to formulate antimicrobial clove essential oil nanoemulsion using microfluidization but also the first to report the chemical stability of clove essential oil after nanoemulsion formation and storage. In addition, the bacterial cell morphology was visualized using a scanning electron microscope and energy dispersive x‐ray spectrometer (SEM‐EDS) to verify the antimicrobial efficiency of clove essential oil nanoemulsion, clove essential oil, and kanamycin sulfate (as control), which has never been reported in the literature.