Influence of essential oils and pectin on nanoemulsion formulation: A ternary phase experimental approach

A pseudo-ternary phase experimental approach was used to model the influence of the mixture components concentration on the nanoemulsions properties as ternary systems. For this, several types of essential oils (EO) were used as lipid phase, being oregano (OR-EO), thyme (TH-EO), lemongrass (LG-EO) and mandarin (MN-EO), while pectin and Tween 80 were studied as emulsifiers. All formulations were processed by microfluidization at 150MPa and 5 cycles. Polynomial models were fitted to experimental data and their adjusted R-2 and p-values were obtained. Remarkably, a pectin concentration of 1% (w/w) allowed the formation of submicron emulsions between 350 and 850 nm in the absence of Tween 80 for all the studied EOs, thus confirming its emulsification capacity. In general, increasing the pectin concentration up to 2% (w/w) enlarged the particle size of emulsions and their viscosity thus suggesting decreased emulsification efficiency during microfluidization. Nonetheless, nanoemulsions with particle sizes below 500 nm were obtained when a minimum Tween 80 concentration of 1.8% (w/w) was used, regardless the pectin or EO concentrations. The modest decrease in the zeta-potential that was observed depending on the type of EO at increasing pectin concentrations indicated that pectin is not or weakly adsorbed at the oil-water interface. All nanoemulsions were transparent at high surfactant and low EO concentrations due to a weak light scattering of the nano-sized oil droplets. Thus, this work contributes in elucidating the role of pectin and small molecule non-ionic surfactants on the formation of submicron emulsions and nanoemulsions containing essential oils. (C) 2018 Elsevier Ltd. All rights reserved.