Physicochemical stability and in-vitro bioaccessibility of concentrated γ-Oryzanol nanodispersions fabricated by solvent displacement method

Abstract

Concentrated γ-Oryzanol nanodispersions were fabricated using milli-Q water (no emulsifier) or 0.1% (w/w) polysorbate 80 (T80), modified lecithin (ML) or sodium caseinate (SC) as emulsifiers. The freshly prepared nanodispersions had comparable particle diameter (118 to 157 nm), γ-Oryzanol concentration (1.75 to 1.92 mg mL^-1) and free-radical scavenging activity (59 to 62%) and had negative ζ-potentials (-22 to -59 mV), indicating that both γ-Oryzanol and emulsifier coexisted on the particles' interface. The nanoparticles had superior physicochemical stability up to 30 days of storage at 5 °C and were successfully autoclaved without excessive growth or aggregation. Nevertheless, they showed distinct physical stability upon storage at specific environmental conditions, which affected their In-vitro gastrointestinal digestion. Comprehensively, emulsifier-free nanodispersions were sensitive to acidic pH, NaCl and CaCl₂ addition. ML and SC coated nanoparticles were sensitive to Ca²⁺ ions, while T80 stabilized nanodispersions resisted to all environmental stresses, resulting in optimal simulated intestinal absorption.

Keywords: Bioaccessibility; Nanodispersion; Physicochemical stability; Solvent displacement method; γ-Oryzanol.