I remember as a child peeling an orange and the zesty aroma remaining on my hands for hours. Little did I know I was experiencing the aromatic qualities of essential oils as I burst the tiny pockets of oil cells in the rind. Hidden inside many plants and citrus fruits are natural compounds that release oils when put under pressure or through the correct extraction method.
Over time, the process of extracting essential oils has changed and differs depending on the plant or flower. If you have ever wondered how essential oils are produced, let's take a look at the five most common methods.
The expression method is used to extract essential oils from the citrus family. The rinds of the fruit are pricked to puncture the cells and then soaked in warm water. After soaking, the rinds are squeezed until the oil is released. Citrus oil does not respond well to heat. The oil must be cold-pressed out of the fruit, known as the expression method. The pressed liquid is then separated into juice and essential oil. Citrus peels are easy to obtain and readily available, making these oils less expensive than other botanicals.
Enfleurage is one of the oldest methods of essential oil extraction. It was popular in France in the 19th century but is not commonly used today. The method uses fat (vegetable or animal) to absorb the essential oils. The technique extracts oils from the most delicate of flowers, such as jasmine and frangipani. Petals and fragrant parts of the flowers are placed in the fat for several days, and this process is repeated with fresh flowers until the fat is infused with fragrance. When the fat is saturated with aroma, it is washed with alcohol to separate the botanical extract from the remaining fat. The oils attach to the alcohol, and then the alcohol is left to evaporate, which leaves the aromatic oil.
The maceration process is similar to enfleurage as it uses vegetable oil to absorb the aromatics from plant material. Instead of placing flowers on the fat, plants and other parts of the flower are dried and crushed to rupture the oil cells and then placed in warm vegetable oil. This type of process is also called the infusion method. Plant material needs to be as dry as possible, and other oils such as vitamin e or wheat germ oil are added to prevent rancidity. The vegetable oil absorbs the fragrant oil, and then the plant material is strained. Fresh plant material is added, and the process is repeated until the desired concentration is reached.
The steam distilled method is the most popular method for essential oil extraction. Up to 93% of essential oils are produced using this process. The plant is placed in a still, and pressurised steam releases the oil by bursting and breaking down the plant's cell structure. The aromatic oil is released and goes through a condensation and collection process where the oil and water separate. When the liquid cools, the oil floats on the top of the water and is collected.
The solvent extraction method is mainly used for delicate botanicals that do not tolerate heat or steam distillation, such as jasmine or rose. The process uses solvents or chemicals which absorb the essential oil. The solvent is then removed through a gentle heat that leaves behind the aromatic molecules. The remaining extract is cooled and mixed with pure alcohol to extract the oil. Solvent extraction is slightly different from other methods, as the residue from the chemicals remains in the oil. These kinds of oils are called absolutes, and although they will have traces of chemicals, it results in a more delicate fragrance, which is used in the production of perfume.
With all that information now in mind, what do you think about the production methods used to extract essential oils? Have you ever tried using any of these methods yourself at home? Let us know in the comments!