High internal phase emulsions stabilized by rice protein-xanthan gum complexes: Interfacial interactions, formation mechanisms, and functional properties

This study investigated the noncovalent interactions between rice protein and xanthan gum (RP-XG) and their effects on the stability of high internal phase emulsions (HIPEs). The infrared spectrum and fluorescence spectroscopy revealed that RP-XG was formed by hydrogen bonding, hydrophobic, and electrostatic interactions. The zeta potential absolute value and solubility of RP-XG increased significantly with rising XG concentration. At an XG concentration of 0.4%, the RP-XG complex exhibited optimal emulsifying performance, with EAI of 23.21 m 2 /g and ESI of 102.29%, the three-phase contact angle approached 90°, with biphasic wettability. Therefore, RP-0.4%XG was selected as the emulsifier for HIPE stabilization in subsequent experiments. The droplet size and rheological behavior of the HIPEs were closely related to emulsifier concentration and oil phase volume fraction. Specifically, the emulsion stabilized with 35 mg/mL RP-XG displayed the smallest droplet size and a dense network structure. Rheological analysis demonstrated that the HIPEs behaved as shear-thinning viscoelastic solids, showing the highest viscoelasticity at an emulsifier concentration of 35 mg/mL and an oil volume fraction of 77%. These findings provided a new strategy for the application of protein-polysaccharide complexes in food-grade HIPEs.