Preparation and characterization of concentrated γ-Oryzanol nanodispersions by solvent displacement method: Effect of processing conditions on nanoparticles formation

Concentrated gamma-Oryzanol nanodispersions were prepared by solvent displacement method, using purified water (no emulsifier) or aqueous solutions of polyoxyethylene (20) sorbitan monooleate (T80), modified lecithin (ML) or sodium caseinate (SC) as emulsifiers. The nanodispersions had comparable particle sizes (126-157 nm), particle size distribution (monomodal), polydispersity index (< 0.1), gamma-Oryzanol concentration (1.69-1.82 mg mL(-1)) and encapsulation efficiency (89.39-98.78%) at optimized processing conditions. Moreover, they had negative zeta-potentials, independently of the composition of the aqueous phase added, indicating that both gamma-Oryzanol and emulsifier contributed to nanoparticles formation. Comprehensively, emulsifier-free nanodispersions had zeta-potential of -46.7 mV, originating potentially from the dissociation of hydroxyl groups of caffeic acid and/or ferulic acid on gamma-Oryzanol structures. ML and SC provided negative charges as expected, while T80 stabilized nanoparticles were also charged (-26.0 mV) despite the absence of ionizable groups on polysorbate structure. These results feature the self-stabilizing properties of gamma-Oryzanol in concentrated colloidal systems, such as nanodispersions, and present a novel approach for its encapsulation in caloric-free formulations.

Automated summary

Concentrated gamma-Oryzanol nanodispersions were successfully prepared using different emulsifiers, showing consistent particle sizes, encapsulation efficiency, and polydispersity index. The study indicated that the dissociation of hydroxyl groups on the structures of gamma-Oryzanol may contribute to the negative zeta-potentials of the nanoparticles.