Extraction Methods of Essential Oils From Herbs and Spices
This chapter describes both conventional and non-conventional extraction methods of essential oils (EOs) from herbs and spices. Although hydrodistillation, steam distillation and solvent extraction are the most applied methods, several non-conventional technologies have been evaluated, especially in respect to EO recovery, and a great potential has been attributed to these non-conventional methods. For instance, ultrasound, microwave, supercritical fluid, pulsed electric fields, ohmic-heating and microwave (MW) extraction techniques applied alone or combined with other techniques are potent tools to obtain EOs in a 'green' way from natural resources such as aromatic plants, spices, fruits and flowers in shorter times and with high extraction efficiency as with conventional processes. Amongst MW extraction methods, vacuum MW hydrodistillation (VMHD), MW hydrodiffusion and gravity (MHG) and solvent free microwave extraction (SFME) were the most applied. Moreover, these techniques have the potential to reduce the energy cost and wastewater and perform in some cases even a solvent-free extraction.