Strategies for reducing Ostwald ripening phenomenon in nanoemulsions based on thyme essential oil.

White thyme essential oil, which can be incorporated in clean-label and food emulsion-based products, is a natural antimicrobial agent. However, emulsions containing essential oils commonly undergo Ostwald ripening as the main destabilization process. The main objective of this work was to evaluate different inhibition strategies for Ostwald ripening to develop stable nanoemulsions containing white thyme essential oil as food preservative and Kolliphor EL as surfactant.In a first approach, the influence of the surfactant/dispersed phase ratio and the number of cycles through the microfluidizer on droplet size distribution were evaluated. Unfortunately, these emulsions underwent Ostwald ripening, which was demonstrated by the application of the Lifshitz-Slyozov-Wagner theory. In order to reduce this destabilization mechanism, two different techniques based on the modification of the formulation (addition of rosin gum or Aerosil COK 84) were analysed by laser diffraction and multiple light scattering techniques. The addition of rosin gum partially inhibited the Ostwald ripening mechanism but only partially. Conversely, the incorporation of Aerosil COK 84 to the continuous phase led to a gel-like rheological behaviour which seems to practically avoid Ostwald ripening.Aerosil particles cover the droplets and form a 3D-network suggesting a Pickering stabilization, which was proved by Transmission Electronic Microscopy. This work confirmed the role of Aerosil COK 84, not only as a thickener or gelling agent, but also as an Ostwald ripening inhibitor. This article is protected by copyright. All rights reserved.