Formulation of Antimicrobial Edible Nanoemulsions with Pseudo-Ternary Phase Experimental Design

The aim of the present work was to study the formulation of edible nanoemulsions containing lemongrass essential oil as an antimicrobial agent, Tween 80 as a non-ionic surfactant and sodium alginate as a stabilizing and texturizing agent, by means of a pseudo-ternary phase experimental design. Polynomial models were satisfactory fitted to experimental data. Nanoemulsions with an average droplet diameter smaller than 100 nm were obtained by mixing oil and Tween 80 at a volume fraction below 0.01 (v/v) and higher than 0.009 (v/v), respectively. However, sodium alginate played a synergistic role regarding the stabilization of oil droplets in the absence of surfactant. In this sense, the higher the sodium alginate concentration, the stronger the negative surface charge of lipid droplets, as well as the higher the viscosity of the mixture. On the other hand, the emulsions' whiteness decreased after increasing the surfactant and decreasing the oil phase, due to weak light scattering. As expected, the antimicrobial activity of blends was greater at higher amounts of essential oil, reaching a maximum of 7.37 log reduction of Escherichia coli after 30 min of contact time. Nevertheless, solubilizing and stabilizing the oil droplets by adding Tween 80 and sodium alginate might enhance the bactericidal effect of essential oils due to an improved dispersion in the continuous phase. The current work presents relevant information to formulate nanoemulsions incorporating antimicrobial agents for food applications.