Pickering emulsions formation using kaolinite and Brazil nut oil: particle hydrophobicity and oil self emulsion effect

In this work, we investigate the role of kaolinite plate-like crystals in the stabilization of emulsions containing Brazil nut oil (Bertholletia excelsa), a natural component that is highly employed in the cosmetic industry as moisturizing and emollient agent. Initially, the interaction of kaolinite with Brazil nut oil and water was investigated. The results revealed a reduced contact angle (CA) with hydrophobic solvents, displaying a low apparent CA with oil (24.8 +/- 3 degrees) and a dominant dispersive component. The hydrophobic character of the siloxanic side of the kaolinite layers favored the ability in adsorbing onto o/w droplets, enhancing emulsion stabilization as a function of particle concentration for a period longer than 7 days. The small content of non-esterified fatty acid present in the Brazil nut oil, based on acidity index (1.24 +/- 0.5wt%), was responsible for some self-emulsion at higher oil fraction and interfere in the kind of emulsion formed due to kaolinite adsorption and due to self-emulsification. The emulsion organization was analyzed by fluorescence confocal microscopy that demonstrated kaolinite plate-like particles deposited throughout the water/oil interface. Altogether, the results confirmed the particles' ability to irreversibly adsorb and stabilize the emulsions. [GRAPHICS] .