Rice protein-based gel particles for Pickering emulsion

Rice protein is a promising plant-based alternative to animal proteins due to its hypoallergenic nature and well-balanced amino acid composition. However, its inherently poor emulsifying properties limit its application as an emulsion stabilizer. This study presents a novel strategy to overcome this limitation by developing food-grade Pickering stabilizers through complexation of rice protein isolate (RPI) with -carrageenan (C) to form gel particles (RPI/C). The primary aim was to create and characterize rice protein-based gel particles suitable as Pickering stabilisers, evaluating their structural and functional performance in emulsions. By optimizing the concentrations of RPI and kappa-carrageenan, gel particles with a size of 0.63 +/- 0.05 mu m and a contact angle of 88.2 degrees +/- 4.6 degrees were obtained. Fourier transform infrared (FT-IR) spectroscopy confirmed hydrogen bonding as the primary interaction between RPI and kappa-carrageenan. The resulting Pickering emulsions supported high oil volume fractions of up to 70 %, with confocal microscopy revealing a dense stabilizing layer formation at the droplet interface. Increasing the oil fraction from 30 % to 70 % led to a significant rise in droplet size from 18.7 +/- 1.4 mu m to 45.3 +/- 4.0 mu m, alongside enhanced viscosity and network strength. Notably, the emulsions exhibited stability for up to six weeks and maintained structural integrity under 200 mM ionic strength. These findings demonstrate the feasibility of RPI/C gel particles as a novel food-grade Pickering stabilizer, broadening the potential applications of rice protein in edible emulsion-based delivery systems.