Separation of Roselle (Hibiscus sabdariffa L.) Seed Oil Using Supercritical CO2 + Ethanol Mixture and Its Quality Analysis

Seeds of roselle (Hibiscus sabdariffa L.) are a good source of protein and carbohydrates, as well as functional ingredients, including the α-tocopherol and oleic–linoleic group of fatty acids. The roselle seed oil extraction process was standardized for supercritical fluid extraction (sc-CO₂) and compared with solvent extraction using n-hexane. A response surface approach was used to evaluate the effect of operating conditions, namely, pressure (10, 15, and 20 MPa), extraction time (150, 165, and 180 min), temperature (45°C, 55°C, and 65°C), and particle size (400, 600, and 800 μm). The oil yield percentage of roselle seed oil extracted by sc-CO₂ was found to be about 16.28% ± 1.07%, obtained at optimum conditions of 20 MPa, an extraction time of 165 min, a temperature of 45°C, and a particle size of 400 μm. The extracted oil was found to be rich in unsaturated fatty acids (74.08% ± 1.43%) with a total phenolic content of 28.60 ± 0.42 mg GAE/g, α-tocopherol of 68.03 ± 1.03 mg/100 g, and a DPPH radical scavenging capacity of 67.93% ± 4.41%.