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

Abstract Concentrated γ-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), γ-Oryzanol concentration (1.69-1.82 mg mL-1) and encapsulation efficiency (89.39-98.78%) at optimized processing conditions. Moreover, they had negative ζ-potentials, independently of the composition of the aqueous phase added, indicating that both γ-Oryzanol and emulsifier contributed to nanoparticles formation. Comprehensively, emulsifier-free nanodispersions had a ζ-potential of -46.7 mV, originating potentially from the dissociation of hydroxyl groups of caffeic acid and/or ferulic acid on γ-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 γ-Oryzanol in concentrated colloidal systems, such as nanodispersions, and present a novel approach for its encapsulation in caloric-free formulations.