Comparative analysis of supercritical CO2, hexane and isopropanol extraction methods for rice bran oil: cultivar-specific assessment for bioactive compound preservation.

BACKGROUND: Rice bran, a valuable rice milling by-product, is rich in edible oil with γ-oryzanol, tocopherols, tocotrienols and phenolics. However, the effectiveness of extraction methods in maximizing oil recovery at the same time as preserving these bioactives across rice cultivars remains unclear. This study compared the extraction of five Egyptian rice cultivars using supercritical CO2, hexane and isopropanol. RESULTS: Rice bran from Giza 179, Giza 178, Super 300, Sakha 108 and Egyptian Yasmine harvested during the 2023 and 2024 seasons was extracted using a split-plot design with three replications. Cultivar, extraction method and their interaction significantly affected crude oil yield, iodine value, saponification number, total phenolic content, γ-oryzanol, tocopherols, tocotrienols and total tocols. Sakha 108 exhibited the highest crude oil content (21.93%) and superior bioactive compound concentrations among the cultivars. SC-CO2 extraction produced the greatest oil yield (24.64%), which was approximately 27% higher than hexane extraction, at the same time as preserving the highest concentrations of total phenolics (22.21 mg gallic acid equivalents g-1 oil), γ-oryzanol (27.64 mg g-1 oil), tocopherols (324.76 mg g-1 oil), tocotrienols (518.54 mg g-1 oil) and total tocols (843.29 mg g-1 oil). Strong positive correlations were observed among vitamin E compounds (r = 0.995) and between bioactive compounds and oil quality traits. CONCLUSION: SC-CO2 extraction, when paired with the Sakha 108 cultivar, achieved the best balance between oil recovery and the preservation of bioactive compounds. These findings underscore the importance of cultivar-specific extraction strategies and support SC-CO2 as a promising green technology for producing high-quality rice bran oil. © 2026 Society of Chemical Industry.