A Comparative Study on the Efficiency and Sustainability of Rice Bran Oil Extraction Methods

Rice bran, a rice milling by-product, is a rich source of bioactives such as tocopherols and γ-oryzanol, with promising antioxidant properties. This study compared three extraction techniques-Soxhlet, maceration, and supercritical CO₂ (SC-CO₂)-to identify the method offering the best balance of rice bran oil (RBO) recovery, composition, and sustainability. Although all methods yielded similar oil quantities (~9.5-10.8%), SC-CO₂ extraction achieved superior preservation of bioactives, with the highest tocopherol (116.9 µg/g) and γ-oryzanol (13.2 mg/g) levels. Antioxidant capacity, assessed via FRAP, ABTS, and DPPH assays, was consistently higher in SC-CO₂-extracted oil. The fatty acid profile further confirmed the advantages of SC-CO₂ extraction, with the oil showing a high proportion of unsaturated fatty acids (86.3%) and low saturated content (13.6%). In contrast, Soxhlet- and maceration-extracted oils contained higher saturated fractions (56.5% and 60.1%, respectively) and lower unsaturated content, reflecting the impact of thermal and solvent exposure on the lipid composition. Environmental impacts were quantified through cradle-to-gate life cycle assessment (LCA), showing that SC-CO₂ extraction led to the lowest ecological burden due to its solvent-free process and lower energy demand. Normalizing impacts on both oil yield and bioactive content further highlighted its advantages. These findings place SC-CO₂ extraction as a green, efficient alternative for valorizing rice bran, yielding a high-quality, antioxidant-rich oil suitable for food and cosmetic applications. The integrated chemical and environmental evaluation underscores the potential for a sustainable bioeconomy, effectively turning agricultural residue into functional ingredients.