Cosmetic creams with caprylic acid-based Natural Eutectic Solvents: Stability, rheology and user perception

This study investigates the impact of hydrophobic Natural Eutectic Solvents (NES) on the physicochemical and sensory characteristics of cosmetic creams. The aim is to assess their potential as innovative, sustainable ingredients introduced directly into the oily phase of an oil-in-water emulsion prior to emulsification.

Four NES formulations, composed of natural components such as caprylic acid, lauric acid, menthol and 1,3-propanediol were incorporated at 10% wt. into a COSMOS-compliant cream chassis. The resulting creams were evaluated for physical stability using static multiple light scattering (Turbiscan®), rheological behaviour via shear and oscillatory tests, and sensory attributes through a trained panel.

Among the four NES-containing creams, three formulations demonstrated satisfactory physical stability over 30 days under accelerated ageing conditions. Menthol-based NES induced phase separation, correlating with increased droplet size and higher Turbiscan Stability Index values. All creams exhibited shear-thinning behaviour, with viscosity profiles and yield stress varying depending on NES composition. Sensory analysis revealed that NES significantly influenced key attributes such as odour intensity, spreading, pick-up and firmness.

Hydrophobic NES can be successfully integrated into the internal phase of cosmetic creams, influencing both their structural and sensory properties. These findings highlight their potential as multifunctional and eco-friendly ingredients in cosmetic formulation, supporting the development of more sustainable, more performant skincare products.