Supercritical carbon dioxide extraction: Lipid composition and carotene content of used activated bleaching oil in Thailand

Used activated bleaching earth (UABE) from palm oil refining contains significant residual oil and bioactive compounds, offering a potential resource for value-added recovery. This study explores the extraction of oil, carotenoids, and vitamin A from UABE using supercritical carbon dioxide (SC-CO₂) under optimized conditions. The highest oil yield (29.36 ± 0.99 %) was achieved at 35°C, 250 bar, and 120 min, with methanol as a co-solvent. The extracted oil exhibited a fatty acid profile similar to crude palm oil, with 49.88–53.22 % saturated fatty acids, primarily palmitic acid (41.39–45.54 %), and 39.45–40.52 % monounsaturated fatty acids, predominantly oleic acid (39.09–40.25 %). Additionally, the carotene content was 85.74 ± 0.16 mg/kg, with β-carotene at 9.57 mg/kg and vitamin A at 159.55 µg/100 g. The study confirms SC-CO₂ as an effective and environmentally friendly extraction technique, yielding high-quality oil and bioactive compounds. The extracted oil has potential applications in the food, energy, cosmetic, and pharmaceutical industries. In addition, regenerated UABE can be reused for palm oil bleaching, supporting sustainability in waste management. Using methanol as a co-solvent significantly enhances oil extraction efficiency and helps preserve high-value bioactive compounds, making it a promising method for sustainable UABE valorization. However, for consumer safety and environmental sustainability, ethanol is recommended as the co-solvent for SC-CO₂ extraction in commercial-scale industrial applications.