How are the essential oils extracted?
Essential oils are natural aromatic extracts derived from plant materials including grasses, leaves, flowers, needles, twigs, peels, seeds, bark and roots. For example, rose essential oil comes from the flowers, basil from the leaves, lime from the peel, fennel from the seeds, sandalwood from the wood, frankincense from the resin, and so on.
The Merriam-Webster dictionary defines essential oils as "any of a class of volatile oils which give a plant its characteristic odour, especially in perfumery and flavourings and in aromatherapy". The term "volatile" refers to substances that evaporate readily at room temperature. These volatile oils released by plants are responsible for some of the aromatic odours of flowers and other plants.
Extraction methods
The "true essential oils" can only be extracted by steam distillation or, in the case of citrus oils, by pressing.
Steam distillation
Steam distillation is the most popular method of extracting essential oils.
In this process, the botanicals are placed in a still and pressurised steam is forced through the plant material - imagine using a steam basket on your cooker. The hot steam forces the aromatic compounds to open their pockets. These compounds escape from the plant material and evaporate into the steam.
The steam must be hot enough to release the essential oils without damaging the plant material. The vapour with the essential oils then passes through a cooling system where it condenses into a liquid consisting of essential oils and water. The essential oils are lighter than water and will float to the top, where they are then separated from the water. bho closed loop system,closed loop extraction system,bho extraction equipment The water as a by-product of distillation is called pure dew or floral water.
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The expression method is used for extracting essential oils from the rinds of citrus fruits. But citrus oils do not hold up well when heat is used in extraction so they are usually obtained by a method called expression .
Expression is also known as the "expeller-pressed" or "cold-pressed" method of extraction since no heat is needed to extract the essential oil.
It is mostly used to extract citrus essential oils. In this process, the peels are pricked in order to puncture the cells containing the oils.
The peels are soaked in warm water and the oil is forced from the material under high mechanical pressure.
Steam distillation and pressing are the only two methods of obtaining 'true essential oils'
However, some aromatic scents come from botanicals that cannot be expressed and do not tolerate high temperature steam distillation.
For this reason, many floral aromatic compounds such as neroli (orange blossom), jasmine and rose are obtained using solvents.
Concretes and absolutes.
Concretes and absolutes are similar to essential oils in that they are highly aromatic, concentrated extracts of plants. However, while essential oils must be produced by steam distillation or pressing, concretes and absolutes require the use of solvents for extraction and therefore cannot be called essential oils.
Flowers or other plant materials are treated with chemical solvents (see below). The 'essential oil' of the plant material is dissolved in the solvent, which is removed, leaving a waxy aromatic compound called concrete.
The aromatic oil is extracted from the concrete using ethanol. Once the alcohol has been removed, the remaining substance, called the absolute, is a very concentrated aromatic compound.
Types of solvent extraction.
Similarly, some plant materials, such as vanilla, which is difficult to extract, or jasmine or rose petals, which are too delicate to survive the distillation process, are extracted from their aromatic essences using another method, a process known as solvent extraction.
The process uses petroleum solvents such as petroleum ether, hexane or toluene; alcohol solvents such as methanol or ethanol; or carbon dioxide. When the solvent is added to the plant, it is absorbed and the aromatic compounds are released.
These solvent-extracted compounds are known as "absolute compounds" and are very concentrated. Technically, they should not be called essential oils. They are either extracted using
Petroleum solvents (e.g. hexane)
ethanol solvents
A supercritical carbon dioxide extraction process. This method helps to maintain the integrity of the essential oil components and produces a highly concentrated finished
A different approach to manual extraction can help in the mass production of plant extracts, he called plant extractors; equipment such as closed-loop extractors, distillers, etc. can help you.