Solute and gas assisted mechanical expression for green oil recovery from rapeseed hulls

• Oil recovery from rapeseed hulls was studied and optimized.
• Conventional and alternative technologies were tested and compared.
• Hexane may be replaced by alternative green solvents for oil extraction.
• SAME is a promising way to efficiently extract oil, proteins and polyphenols.
• GAME is efficient to recover oil from hulls without using organic solvents.

This work aims at evaluating the alternative technologies of solvent (liquid) and gas assisted mechanical expression to recover oil from rapeseed hulls and comparing these technologies with conventional solute extraction (SE). First, SE and solute assisted mechanical expression (SAME) have been applied using hexane and green solvents (water, ethanol, water/ethanol mixture) to extract efficiently oil and other bioactive compounds (polyphenols, and proteins). In order to avoid the use of organic solvents, oil extraction yield was compared to that of gas assisted mechanical expression (GAME) technology after optimizing the extraction parameters (effective pressure, CO2 flow, and the impact of pre-treatments (grinding and/or cooking)). Results show that the highest extraction yield (65%) with GAME was obtained using 35 MPa effective pressure, 8.5 kg/h CO2 flow, and without pre-treatment. Although similar extraction yields have been recorded between the three extraction processes, the use of GAME technology allowed the recovery of oil without subsequent purification steps (removing the extraction solvent, meal desolvation), and without pre-treatment.