High-Internal-Phase Pickering Emulsions Stabilized by β-Lactoglobulin Nanoparticles: Effects of Rheology, Stability, and Aging

Abstract High-internal-phase Pickering emulsions have found a greater potential in food industry. β-Lactoglobulin (BLG) is a major component of whey protein and is of interest due to its easy availability, nutritional benefits, and potentially stabilizing properties. Here, we present our work on Pickering high-internal-phase emulsions (HIPEs) with a dispersed-phase oil fraction of 75 wt %, stabilized using BLG nanoparticles. These nanoparticles were prepared using an antisolvent precipitation technique, eliminating the need for any external cross-linking agent. The present work focuses on stability of Pickering HIPEs, specifically on the effects of particle and salt concentration, by employing techniques like small-angle X-ray scattering along with scanning electron microscopy, optical microscopy, light scattering, and rheology. Given that Pickering HIPEs exhibit marked viscoelastic properties, we also employ RheoSAXS to elucidate structural changes of the emulsion under shear. We show that higher particle concentrations (3–5 wt %) can enhance the stability of the emulsions. Furthermore, by measuring the emulsions under different physical conditions (fresh, aged, and aged at elevated temperatures), we show that aging (shelf storage) over a period of 90 days can induce structural changes in the system. Here, we employ combinations of scattering models to understand the structural properties of the emulsions. Our studies show that SAXS, along with rheology, is an effective tool for studying these emulsions with high oil concentrations, providing insight into the structure and behavior of food-grade systems.