Ultraefficient stabilization of high internal phase emulsions by globular proteins in the presence of polyols: Importance of a core-shell nanostructure

We report that oil-in-water (o/w) high internal phase emulsions (HIPEs) can be ultra-efficiently stabilized by globular proteins in the presence of appropriate concentrations of polyols. Using bovine serum albumin (BSA) and trehalose as the model globular protein and polyol, stable HIPE gels at 0.8 oil volume fraction can be easily prepared at a protein concentration in the aqueous phase as low as 0.005 wt% in the presence of 40 wt% trehalose. Higher concentrations of polyols facilitated the formation of finer HIPEs with a stronger gel network associated with a higher extent of droplet bridging. The HIPE gels exhibited excellent coalescence stability against long-term storage or upon extensive heating. The ultra-efficient stabilization of BSA in the presence of trehalose arises from two contributions: facilitated formation of bridged emulsions and interfacial stabilization of trehalose aggregates. The soft particulate nature of BSA in the presence of trehalose was due to the formation of a core-shell nanostructure with trehalose molecules surrounding the protein core. The findings provide a novel and facile strategy to transform globular proteins into outstanding soft particles for stabilizing HIPEs, as well as guiding the development of novel biocompatible and even food-grade HIPEs with promising applications in the food, cosmetics and pharmaceutical fields.