Preparation of liposomes encapsulating β–carotene using supercritical carbon dioxide with ultrasonication

β –Carotene-loaded liposomes were prepared utilizing ultrasonication and supercritical carbon dioxide (SC-CO₂) as an alternative to organic solvents. Thermally Z–isomerized β–carotene samples containing 2.4, 37, or 87 % Z–isomers were fed with hydrogenated soy phosphatidylcholine. Pressure and temperature were changed in ranges 10–25 MPa and 50–70 °C, respectively, and isomerization ratio was changed. Transmission electron microscopy revealed ∼90–150 nm spherical liposomes. Ultraviolet–visible spectroscopy indicated that β–carotene aqueous nanosuspensions formed more effectively when Z–isomer-rich β–carotene was used as a starting material. Zeta potentials indicated that soy-phosphatidylcholine-based Z–isomer-containing β–carotene aqueous nanosuspensions showed good stability.