Statistical simplex centroid experimental design and formulation maps to predict the stability in cosmetic emulsions containing commercial emulsifiers

Formulating cosmetic products to meet consumer expectations poses significant challenges in terms of stability and shelf life. This work evaluates cosmetic emulsions formulated with three commercial emulsifiers: Polyglyceryl-3 distearate (Dermofeel®, a biobased surfactant), Glyceryl stearate (50%)/PEG-100 stearate (50%) (Lipomulse®, a nonionic mixture of glyceryl and ethoxylated surfactants), and Potassium cetyl phosphate (Amphisol K®, an anionic surfactant). Additionally, three emollients, namely Caprylic/Capric Triglyceride, Isoamyl Cocoate, and Jojoba Oil, were incorporated into the formulations. The effect of emulsion composition on stability, droplet size, rheology, and texture was systematically assessed via experiments and multivariate regression modeling, thereby providing an objective tool for cosmetic emulsions formulation. The lifetime of emulsions showed that emulsions containing Potassium cetyl phosphate exhibited separation velocities larger than 60 μm/s, whereas those with the other emulsifiers showed separation velocities below 40 μm/s, indicating larger lifetimes. A predictive model based on a statistical simplex centroid experimental design was developed to evaluate the separation velocity of emulsions based on the composition of the system, enabling the assessment of important variables that influence emulsion stability. The results indicate that composition variables (such as oil concentration) and formulation variables (such as surfactant nature and oil type) are important in determining emulsion stability, but also secondary effects such as surfactant-emollient interactions are crucial to predict the lifetime of cosmetic emulsions.