Subcritical water-treated soy protein-gum Arabic core-shell nanoparticles as phytosterol carriers

Summary Soy protein-gum Arabic (GA) core-shell nanoparticles were fabricated as carriers for hydrophobic phytosterol (PS) using an anti-solvent precipitation (pH 7.0) and then coating GA on the surface of protein-based PS nanoparticles at pH 4.5. PS nanoparticles stabilised by heat-treated soy protein isolate (SPI), especially subcritical water-treated SPI (SW, 120 °C), exhibited higher encapsulation efficiency (EE), loading amount (LA) and colloidal stability than native SPI-stabilised PS nanoparticles. The highly flexible conformation and more exposed hydrophobic clusters of SW-treated SPI could result in a quick encapsulation of more PS into the interior of protein molecules during anti-solvent precipitation. However, for native SPI with rigid globular structure, the loading of PS mainly occurred on the surface hydrophobic sites of protein molecules. After introducing GA (≥5 mg mL −1 ) to PS nanoparticles fabricated by SW-treated SPI, submicron-sized ( D h 250.71~341.76 nm) core-shell nanoparticles with high acid solubility and thermal stability were formed. The coating of GA decelerated the digestion of SW-treated SPI, and improved the EE, LA and in vitro bioaccessibility of PS under acidic environment. These results reveal the protein structure dependence of PS encapsulation and provide a simple approach to fabricate biopolymer-based nanoparticle delivery system for hydrophobic bioactives in acidified functional drinks.