Impact of Fatty Acid Composition of Polyglycerol Esters on the Emulsifying Performance in Cosmetic Formulations

The cosmetics industry continually seeks innovations that deliver ever-higher performance while meeting growing sustainability requirements. Although numerous plant-derived surfactants have recently emerged, achieving performance levels comparable to synthetic benchmarks remains challenging. In this study, we aimed to design a natural polyglycerol-10 ester (PG-10 ester) capable of stabilizing demanding systems such as high-internal-phase nano-emulsions (nano-HIPE) and mineral oil-in-water sunscreens. We investigated the key parameters governing surfactant efficiency: fatty acid composition from C12 to C22 or their blends, the presence of partial glycerides, and reaction parameters. Various polyglycerol esters were synthesized and characterized through chromatographic analysis and HLB determination, and then incorporated into formulations to assess their performance. This work made it possible to identify four parameters as essential for achieving high surfactant efficiency: (i) grafting multiple fatty acids onto a single polyglycerol backbone, (ii) combining short/medium-chain (<C16) and long-chain (≥C16) fatty acids, (iii) including partial glycerides within the surfactant, and (iv) allowing the reaction medium to reach full equilibrium. Achieving full equilibrium results in synthesis medium clarity, which allows the HLB value to rise from 6 to 7 to 11–12 and ensures complex emulsion stability. This rational design approach led to a natural PG-10 ester whose performance equals that of conventional synthetic benchmarks, providing a significant advancement toward sustainable high-performance surfactant technologies.