Extraction of high-value lipids and phenolic compounds from sorghum bran via a sequential supercritical carbon dioxide approach

Sorghum bran, containing high-value lipids and phenolic compounds, is an underutilized food processing byproduct. This study developed and optimized a green method based on a sequential pure supercritical carbon dioxide (SC–CO2) and ethanol/water-modified SC–CO2 extraction to extract wax-rich lipids and phenolic compounds from sorghum bran in a single step. The extraction conditions, namely, temperature (20–100 °C), pressure (20–40 MPa), extraction time (0.5–5 h), and cosolvent type (ethanol or ethanol–water), were optimized for the highest wax-rich lipids and phenolics extraction yields. In the first part, neat SC–CO2 at 40 MPa and 60 °C resulted in the highest lipid yield (6.2%, w/w dry basis), which contained ∼5% (w/w) high-melting point waxes. The purified wax fractions containing phytosterols showed high melting points of 57–87 °C. In the second part, the highest total phenolics and flavonoids yields were achieved at 40 MPa and 40 °C via 15% (w/w) ethanol–water (1:1, v/v) modified SC–CO2 by 150 ± 3 mg of gallic acid equivalent (GAE)/100 g of bran (dry basis) and 99.6 ± 4 mg of catechin equivalent (CAE)/100 g of bran (dry basis), respectively. Overall, this study provides a novel single-step extraction approach based on SC–CO2 to extract and fractionate lipids and phenolic compounds from sorghum bran