An essential oil is a concentrated, hydrophobic liquid containing volatile aroma compounds from aromatic plants. They are also known as volatile or ethereal oils, or simply as the "oil of" the plant material from which they were extracted. The term essential indicates that the oil carries distinctive scent (essence) of the plant, not that it is an especially important or fundamental substance. They are not to be confused with essential fatty acids. They are used in perfumes and cosmetics, for flavoring food and drink, and for scenting incense and household. Interest in essential oils has revived in recent decades, with the popularity of aromatherapy, a branch of alternative medicine which claims that the specific aromas carried by essential oils have curative effects.
Essential oils are generally extracted by steam distillation process. During the distillation process, the essential oil crop is partially dried to reduce the volume of plant material. The wilted or partially dried plant material is loaded in the distilling vessel uniformly so that steam is channeled evenly through the crop during distillation. Firing is done at the bottom of the vessel to convert the water kept at the bottom of the vessel into steam so that when it comes in contact with oil glands of the crops the oil evaporates. The combined steam and oil vapors are channeled into the condenser where cool water is circulated and separates the water and oil.
The oil (otherwise called the ‘distillate’) is collected in the oil receiver. The essential oil accumulates on top of the water in the receiver. The oil is then collected in the separation funnel that separates it from the water. During distillation, the oil receiver must be covered to protect it from dust and contamination. After cleaning the oil is stored in airtight steel or aluminum container to maintain the quality.