Pretreatment strategies in essential oil extraction: mechanistic understanding and comparative insights into yield, composition, and process efficiency

Essential oils (EOs) are valuable bioactive compounds widely used in pharmaceutical, food, and cosmetic industries, yet their recovery from plant biomass is often limited by low yield and prolonged processing. This review critically evaluates pretreatment strategies for enhancing EO recovery, particularly their integration with conventional extraction techniques. A systematic analysis of Scopus-indexed literature from the past decade identified approaches, including enzymatic, microwave, ultrasound, deep eutectic solvent (DES), surfactant, salt, and combined pretreatments. Pretreatment generally improved EO yield, facilitated enrichment of key volatile constituents, and, in some cases, enhanced biological activity by disrupting plant cellular structures and improving mass transfer. However, its effectiveness varied with plant matrix, operating conditions, and pretreatment selection. Combined strategies may provide synergistic benefits but can increase process complexity, obscure individual contributions, and may limit industrial applicability. Thus, systematic optimization and standardization are essential for developing compatible, efficient, and economically viable pretreatment strategies for EO recovery.