Effect of Microfluidization Condition on Physicochemical Properties and Inhibitory Activity of Nanoemulsion Loaded with Natural Antibacterial Mixture

The main objective of this study was to investigate the effects of the microfluidic pressure (600-1200 bar) and cycles (2-4) on the inhibitory activity and physicochemical properties of the nanoemulsion loaded with a natural antibacterial mixture (i.e., citral, trans-2-hexen-1-ol, and linalool, 1:1:1 w/w). The current study showed that the microfluidization at 1000 bar for 4 cycles resulted in the most stable antibacterial nanoemulsion with the smallest droplets. In most cases, the cycle had the more significant effect than the pressure on the physicochemical properties of the antibacterial nanoemulsion. The minimal inhibitory concentrations (MICs) for Salmonella Typhi, Escherichia coli O157:H7, Staphylococcus aureus, and Listeria monocytogenes were 2500, 5000, 1250, and 5000 mu g/ml, respectively. In general, the microfluidization condition did not significantly affect the xi-potential and inhibitory activity of the antibacterial nanoemulsion. The microfluidization at 1350 bar and 3 cycles was the overall optimum preparation condition. There was an insignificant (p > 0.05) difference between the experimental and predicted optimum point. This verified the adequacy of the response surface models fitted for explaining the properties of antibacterial nanoemulsion as a function of microfluidization condition.