Ghassoul-Clay- and Oil-Loading-Induced Colloidal Gelation of Lavender Essential Oil Emulsified Systems

Abstract

Lavender essential oil is a promising bioactive ingredient, but its incorporation into aqueous formulations is limited by its low water solubility and high volatility. This work structured lavender oil-in-water emulsified systems through two approaches: Ghassoul clay incorpo ration and increased oil loading. The standard formulation containing 1.25 wt.% oil showed a narrow droplet size distribution, with a Sauter mean diameter of 114 nm, respectively, and Newtonian behavior with a viscosity of 0.97 mPa·s. Ghassoul addition did not significantly modify droplet size, but induced shear-thinning and gel-like behavior. Zero-shear viscosity increased from 2 Pa·s at 5 wt.% clay to 550 Pa·s at 20 wt.%, while 15–20 wt.% Ghassoul showed the highest resistance to clay sedimentation after 30 days. Increasing lavender oil concentration promoted droplet growth and broader size distributions. The 30 wt.% oil formulation exhibited the strongest droplet-mediated structure, with G′ exceeding G′′ and zero-shear viscosity reaching 156 Pa·s, whereas 40 wt.% oil weakened the network due to droplet coarsening and polydispersity. The results highlight the key role of clay-particle networking, droplet crowding, droplet-size distribution, and viscoelastic structuring in con trolling gel-like behavior and physical stability, supporting the design of essential oil-based colloidal gels for topical, pharmaceutical, or cosmetic delivery applications.