Steam Distillation: Principle and Applications for the Extraction of Essential Oils from Plants

Around 80% of the populace depends on herbal medicines to meet their well-being needs. Subsequently, therapeutic and aromatic plants are significant in light of the fact that the items obtained from plants are utilized to make herbal medicines. The essential oils are used in aromatherapy, a form of an alternative therapy for supporting well-being or health of people. The essential oils exist in the oily form and have a characteristic essence, scent, or aroma of the plant from which it is extracted and the reason the name "essential" is added before its title. The available literature shows that usage of essential oils began more than 2500 years in the Middle East countries. The conventional method of segregating unpredictable mixtures as essential oils is distillation. The boiling point of these oils is usually high, which evaporate near boiling point of water. This forms the basis of using water or steam for distillation methods and was most commonly used method for extraction of essential oils from herbal plants. During this process, the fragments of parts of plants containing volatile oil are exposed to the steam or boiling water, releasing fragrance with oils through evaporation. The volatile compounds are diffused into the vapors of water and transported to the condenser and finally collected in the receiver where they are segregated from the aqueous layer. If dry distillation is attempted, the organic components may tend to decompose. There are many additional advantages of steam distillation method, e.g., the method generates organic solvent-free products; the technology is reliable and involves inexpensive equipment. Nowadays, the advancement in distillation methods improves the yield and quality of essential oils with faster extraction kinetics at lower cost. Microwave-assisted methods and solvent-based extraction methods are also included in this chapter.