Colloidal zein particles at water-water interfaces

We synthesize colloidal zein particles using the anti-solvent precipitation method and study particle behavior at water-water interfaces. When added to phase-separating aqueous mixtures of fish gelatin and dextran, particles accumulate at the interface. In order to explain the mechanism of particle accumulation at the water-water interface, we investigate how zein particles interact with polymers (i.e. fish gelatin and dextran). We show that both polymers adsorb similarly on particle surface, which can explain why particles form contact angles close to 90°. Moreover, we show that particle accumulation is accompanied by aggregation. Those aggregates are able to arrest the late stage of the demixing process of the emulsion by the formation of a stable particle-rich layer at the water-water interface. This layer is referred as a ‘foam-like layer’ due to its morphology similar to that of a wet (non-drained) foam, and contains droplets of one phase, surrounded by particle-stabilized lamellae of the other phase.