Green extraction of hemp seeds cake (Cannabis sativa L.) with 2-methyloxolane: A response surface optimisation study

The extraction of hemp seed oil (HSO) with 2-methyltetrahydrofuran, also known as 2-methyloxolane (2-MeOx), was investigated as an alternative to hexane. Hemp seeds (Cannabis sativa L.) have a high nutrient content with an excellent source of lipids (25–35%) and easily digestible proteins (20–25%). HSO is generally obtained by cold pressing and/or solvent extraction. Commercial hexane is still the reference solvent for the oilseeds extraction industry. However, there is an urgent need to find alternatives, as hexane is highly toxic. 2-MeOx is a bio-based solvent that was added to the list of permitted solvents for foodstuffs and food ingredients production in Europe in January 2023. This study investigated the extraction of HSO with 2-MeOx and the influence of solvent water content (1.1−4.2% water), liquid/solid ratio (2−4 g/g) and temperature (50−65 °C) on extraction efficiency, solvent retention index, residual oil content, total phenolic content, carotene and chlorophyll content. Extraction conditions were optimised using response surface methodology and Box-Behnken design. Optimal conditions were obtained using a solvent with a water content of 1.1%, a liquid/solid ratio of 3, and a temperature of about 60 °C. The predicted optimum values were an oil yield of 12.15 oil/100 g DM, a solvent retention index of 0.205 g/g, a residual oil content of 0.319 g oil/100 g DM, a total phenolic content of 4735 mg GAE/kg oil, a carotene content of 474 μg/g oil and a chlorophyll to carotene ratio of 3.55.2-MeOx proved to be a valuable solvent for the extraction of high-quality HSO.