High internal phase emulsions stabilized by Rice bran albumin-γ-Oryzanol complex for enhanced gel strength and...

This study aimed to improve the ability of rice bran albumin (RBA) to stabilize high internal phase emulsions (HIPEs) by forming complexes with γ-oryzanol (γo). By varying the concentration (0-0.4%) of γo, the HIPEs stabilized by the RBA-γo complexes exhibited distinct mechanical properties and oxidative stability. Contact angle measurements indicated that an appropriate amount of γo (0.2%) enhanced the surface hydrophobicity of RBA. As a result, the proteins were more capable of adsorbing at the oil-water interface. At this concentration, the HIPEs showed higher gel strength, apparent viscosity, and oxidative stability. Confocal laser scanning microscopy revealed a more uniform network structure with a hexagonal-like arrangement, which attributed to formation of stable interfacial film by the RBA-γo complexes that suppressed droplet aggregation via steric hindrance. Furthermore, multi-spectroscopic analysis indicated that γ-oryzanol interacted with RBA mainly through hydrophobic interactions and hydrogen bonding. A moderate amount (0.1-0.2%) of γ-oryzanol addition induced partial unfolding of RBA, as evidenced by decreased α-helix content and increased β-sheet and random coil structures, which enhanced the molecular flexibility of the protein. However, excessive γ-oryzanol led to protein refolding, resulting in decreased mechanical strength and oxidative stability of the HIPEs. This study provides a theoretical basis for the utilization of protein-phytosterol complexes as natural stabilizers in the development of functional HIPEs, which could serve as potential platforms for nutrient delivery systems.