Optimization of the supercritical fluid extraction of Quercus cerris cork towards extraction yield and selectivity to friedelin.

• SFE of friedelin from Quercus cerris cork with pure/modified CO 2. • Experimental conditions tested: 40–60 °C, 0–5 wt% ethanol, 5–11 g C O 2 m i n - 1 . • Optimization of the SFE following DoE and RSM approaches. • Total yield, friedelin concentration and selectivity to friedelin were measured. Optimization of the supercritical fluid extraction of Quercus cerris cork was carried out using Box-Behnken design of experiments and response surface methodology (RSM). The optimized process variables were temperature (T : 40, 50 and 60 °C), ethanol content (EtOH: 0.0, 2.5 and 5.0 wt%) and CO 2 flow rate (Q C O 2 : 5, 8 and 11 g m i n - 1 ). The studied responses were total extraction yield (η T o t a l), friedelin concentration of the extract (C F r i e d e l i n), and selectivity towards friedelin (α F , n F). The linear effect of EtOH was by far the most influent operating condition (Pareto analysis) and the highest yield (η T o t a l = 2.2 wt%) was attained with 5.0 wt% EtOH. The RSM model estimates maximum friedelin concentration in the extracts (38.2 wt%) to occur without cosolvent (0 wt% EtOH) for the lowest T (40 °C) and Q C O 2 (5 g C O 2 m i n - 1 ). As for selectivity, the experimental α F , n F values were always higher than 1.0 and reached 3.1 (at 50 °C, 5 wt% EtOH, 11 g C O 2 m i n - 1 ). Altogether, these results suggest friedelin can be selectively removed from Quercus cerris cork by supercritical fluid extraction within the range of experimental conditions studied. [ABSTRACT FROM AUTHOR]