Preparation of Nanoemulgels Containing Lemon Essential Oil and Pectin: Physical Stability and Rheological Properties

Abstract

Nanoemulgels are novel formulations of great interest for their use as dual-release systems and as fat substitutes in foods. Lemon essential oil, with a large number of benefits due to its antimicrobial, antifungal, and medicinal properties, and low methoxyl pectin, a natural polysaccharide capable of gelling by adding divalent ions such as calcium, are very appropriate ingredients to produce nanoemulgels with potential applications in industries such as cosmetics, agrochemistry, pharmaceuticals, or food. In this work, lemon-essential-oil-in-water nanoemulgels containing low methoxyl pectin derived from citrus peels were prepared following a three-step process that involves the preparation of a nanoemulsion, a pectin gel, and the mixture of both. In the first stage, the stirring time and the rotational rate employed during the mixing step were assessed. Once the preparation protocol was established, the pectin gel/nanoemulsion mass ratio was investigated. Different techniques were combined to evaluate the influence of the processing and the composition variables on the particle size distribution, mean diameters, flow curves, and physical stability of different emulgels obtained. It was found that the processing variables studied, stirring time, and rotational rate, do not influence the mean particle size of the emulgel, with values matching those of the starting nanoemulsion. However, 3 min and 200 rpm were selected for exhibiting the lowest TSI values. Regarding the composition, a higher content of pectin gel caused a higher viscosity, and therefore a higher physical stability, with the 75P/25E emulgel being the most stable. Aggregation of gel particles, because the pectin gel was really a sheared gel, was the main responsible contributor to the results obtained. This work highlights the importance of the preparation and formulation variables to develop stable, innovative formulations based on nanoemulgels.