Transparent high internal phase emulsion gels stabilized solely by proteins

In this work, we report on highly transparent and stable high internal phase emulsions (HIPEs) stabilized by protein in general and globular proteins in particular using a refractive index (RI)-matching technique. Sucrose (50 wt.%) was added in the aqueous phase to match the RI of the oil phase (dodecane). In the presence of 50 wt. % sucrose, gel-like HIPEs (oil fraction of 0.75) could be stabilized by bovine serum albumin (BSA a representative globular protein) at a concentration in the aqueous phase as low as 0.3 wt.%. In addition to achieving high transparency, the presence of 50 wt.% sucrose remarkably improved the emulsification performance of BSA and facilitated the formation of HIPE gels. The improvements were largely associated with high surface coverage via the formation of bridging droplets. The presence of 50 wt.% sucrose transformed BSA into a soft nanoparticle with high structural integrity that could resist the adsorption-induced structural disruption at the interface. The RI-matching strategy to fabricate transparent HIPE gels could be applied to other proteins. The findings are of interest for providing a facile strategy to fabricate biocompatible and highly transparent HIPE gels with great potential in the food, healthcare and light-induced catalysis fields.