Enhancement of physicochemical properties of whey protein-stabilized nanoemulsions by interfacial cross-linking using cinnamaldehyde

The impact of incorporating different levels of cinnamaldehyde (CA) into the oil phase used to prepare whey protein isolate (WPI)-stabilized nanoemulsions was investigated. Stable nanoemulsions could not be formed by pure CA, which was attributed to gravitational separation, but they could be formed from mixtures of CA and triglycerides. The mean particle diameter produced by homogenization decreased with increasing CA, which was attributed to the reduction of oil phase interfacial tension and viscosity. CA enhanced the physical stability of the nanoemulsions to salt addition (0–500 mM) and thermal processing (30–90 °C), but could not prevent droplet flocculation near the protein's isoelectric point (around pH 5). SDS-PAGE and surface load measurements indicated that more protein accumulated at the droplet surfaces in the presence of CA, which was attributed to interfacial crosslinking. CA may therefore be a useful means of modulating the physicochemical properties of protein-stabilized nanoemulsions.