Physiological and antimicrobial properties of a novel nanoemulsion formulation containing mixed surfactant and essential oils: Optimization modeling by response surface methodology

This research aims to optimize the parameters for the production of a stable nanoemulsion containing a mixture of essential oils (EOs) with a surfactant blend (Tween and Span 80) and assess its antimicrobial potency against spoilage bacteria and foodborne pathogens. The impact of a surfactant blend's hydrophilic-lipophilic balance (HLB) as well as surfactant:oil ratio was investigated based on the mean particle size (z-average) and polydispersity index (PDI). Results showed HLB value of 12 and a ratio of surfactant to oil at 0.75:1 exhibited an emulsion with the smallest z-average and PDI. Following this, a response surface methodology (RSM) employing central composite design (CCD) was utilized to formulate an optimal nanoemulsion using the microfluidization (MF) technique. The RSM revealed that the microfluidizer pressure of 15,000 psi and 5 cycles produces a z-average of 38.11 nm, PDI of 0.27, zeta-potential of 37.8 mV, and EE of 83.8%. The comparison between the experimental and anticipated results of the optimized nanoemulsion revealed no significant differences (p > 0.05). The optimal nanoemulsion displayed excellent stability during 30 days of storage at both 4 and 30 degrees C compared to 5 days for coarse emulsion. The nanoemulsion exhibited potent antimicrobial activity, showing minimum inhibitory concentration (MIC) values in the range of 0.019 to 0.156 mu L/mL, surpassing the antimicrobial efficacy of the coarse emulsion, which had MIC values between 0.039 to 0.312 mu L/mL. Thus, this study emphasized the efficacy of RSM design in developing an optimal nanoemulsion with enhanced antimicrobial properties using EOs, making it a promising natural food preservative.