Subcritical water extractions to obtain plant volatile compounds: challenges and opportunities for the essential oils industry

Abstract Plant volatile compounds have been the focus of promising research into alternative approaches to address the limitations of conventional production methods. Subcritical water extraction (SWE), utilising water at temperatures between 100 and 374 °C and pressures up to 220 bar, represents a novel and environmentally friendly approach. This review explores the impact of key SWE parameters on extraction yield and composition. Smaller particle sizes (around 0.50 mm) and higher flow rates enhance yield, while pressure has a relatively limited effect. Increasing the extraction temperature generally improves both yield and selectivity, enhancing the recovery of oxygenated and moderately non-polar compounds. Moreover, SWE promotes more extensive rupture of plant cell walls and the faster transfer of volatile compounds into the solvent, resulting in extracts with a broader chemical profile.