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.