Innovative and ecofriendly methods and pretreatments for essential oil extraction: An update

Abstract

Historically, a variety of essential oils (EOs) have been used for their aroma and flavor as well as for the important biological activities they display, such as antibacterial, antioxidant, antifungal, antiparasitic, antiviral, enzyme inhibitor, and insecticide. Nowadays, EOs have several important applications in the pharmaceutical, food, cosmetic, and agricultural industries. Various investigations have revealed that the composition and quality of EOs can be altered due to the extraction methods and solvent used. The most common extraction methods include hydrodistillation, steam distillation, cold pressing, and solvent extraction. Although these techniques have been known and studied for many years, their application is time-consuming and shows a large number of disadvantages, such as the loss of highly volatile compounds, low extraction efficiency, and possible toxicity due to the presence of residual solvents. As a consequence, and in search of environmentally friendly methods, innovative and alternative techniques are currently available to improve the recovery of these natural products. Most of these methods are based on the degradation or disruption of the plant cell wall to better release the inner components. Among them, we can highlight the use of cellulases, hemicellulases, pectinases, oxidases, and combinations of them as enzymatic pretreatment, the use of supercritical CO2 as an extraction medium, ultrasound, microwave, and ohmic heating-assisted extraction. Recently, the field of biomimetics of enzymes has grown, mainly in the case of oxidoreductases, and the application in the oxidative degradation of the plant cell walls is in the beginning. In this chapter, emergent and eco-friendly pretreatments (and the combination with extraction processes that could be easily applied in large-scale industrial production) have been critically reviewed. Also, insights into the mechanism of action of each process have been discussed. Finally, conclusions, future perspectives, and recommendations have been highlighted in this chapter.