Rice bran oil extraction via supercritical fluids: Composition diversity, process fundamentals, and emerging challenges

With the continuous growth of the global population and the increasing demand for staple foods, rice production is expected to expand, resulting in more extensive rice processing activities and, consequently, greater generation of by-products such as rice bran (RB). Rice bran oil (RBO), extracted from RB, is highly valued for its favourable fatty acid profile and diverse bioactive compounds, positioning it among the healthiest edible oils. The composition of RBO, particularly its fatty acid profile, is influenced by several factors, including rice variety, geographical origin, climate conditions, and processing methods. Supercritical fluid extraction (SFE), particularly using carbon dioxide (CO₂), has emerged as a green and efficient approach for RBO extraction. This technique offers notable advantages over conventional methods by preserving heat-sensitive bioactive compounds, improving oil quality, and minimising environmental impact. Several parameters are critical in determining the efficiency of SFE, with reported ranges in the literature including temperature (40 – 80 °C), pressure (25 – 50 MPa), CO₂ flow rate (0.01 – 1.0 L/min), co-solvent concentration (0.4 – 30 %), particle size (14–1670 µm), and extraction time (30 – 120 min). Pre-treatment techniques, such as drying, germination and enzymatic treatment, can facilitate oil release from the bran matrix and enhance the recovery of nutritionally valuable compounds. The potential of SFE to support sustainable RBO production underscores this review, which focuses on the compositional, technological, and strategic aspects of RBO extraction, with particular emphasis on its role in advancing zero-waste initiatives.