Essential oils are extracted from certain varieties of tress, herbs, grasses roots, fruit and flowers. The oil is concentrated in different parts of the plant. The oil is extracted in a variety of ways, most common being steam distillation; other methods include CO2 extraction, Solvant extraction, Maceration, Enfleurage and Cold Process extraction. The method of extraction affects the quality of essential oils. Some methods are better suited for certain plants as compared to others.
Nearly all essential oils are extracted using physical extraction method, while most of the essential oils are extracted using two methods steam distillation of plant materials; and cold pressing of fruit peels. Nowadays very few essential oils are obtained using chemical solvent extractions and are termed as “extracts”.
Steam or water distillation: Steam distillation is the most popular method used to extract essential oils from plants to use in natural products. In this process water or hot steam is passed through the plants, pulling the essential compounds away from the plant matter. The end product of this process gives pure essential oil and floral water.
Cold-Press Extraction: This method is also known as Expression or Scarification and is particularly used for Citrus peels. This process works by mechanically pressing or squeezing plant matter to cause it to release essential juices or oils.
Solvent Extraction: This method uses food grade solvents like ethanol and hexane to isolate essential oils from plant material. This method is best suited for plants materials that yield low amount of essential oil, are largely resinous or are delicate to withstand the pressure and distress of steam distillation process.
In this process, non volatile plant material such as waxes and pigments are also extracted and are sometimes removed through other processes. Once the plant material is treated with the solvent, it products a waxy aromatic compound called “Concrete”. When this concrete substance is mixed with alcohol, oil particles are released. The only disadvantage is that the chemicals used in process remain in the oil. The end product of this process is commonly known as “Absolute” and cannot be termed as essential oil. The main difference between essential oil and an absolute, is that absolutes contain a predominance of heavier, non volatile molecules and are thus more viscous than essential oils.
Solvent extraction encompasses the following methods:
- CO2 extraction
- Co2 Extraction: It is relatively a new method and produces a higher quality oil as none of the constituents of the oil are damaged by heat. In this method, CO2 is used as a solvent and operates at temperature between 95 to 100 degrees F whereas, steam distillation operates between 140 to 212 degrees F. In steam distillation, as a result of the temperature applied, the molecular composition of both the plant matter and essential oil is changed. However, a CO2 extract gives a closer chemical composition of the original plant from which it is derived as it contains a wider range of the plants constituents.
CO2 extracts are usually thicker than their essential oil counterparts and often give more aroma of the natural herb, spice or plant than the distilled essential oil. M
- Maceration: Maceration is the process used for manufacturing infused oils. They are manufactured when carrier oils are used as solvents to extract therapeutic properties from plant material.In this process, finely chopped plant material is mixed with base oil such as Olive, almond or sunflower oil and placed in a tight vessel for a week, only shaken occassionly. The liquid is then strained and the solid residue is pressed to recover any remaining liquid.Strained and expressed liquids are then mixed and clarified. Once the maceration process is complete, the base oils usually changes its colour.
The benefit of a macerated oil over distilled oil is that this process captures heavier, larger plant molecules as compared to the ones captured through distillation process and thus the oil has more plant’s essence. Some examples of infused oils are calendula and carrot oil.
- Enfleurage: Enfleurage is an ancient method of extraction which is based on the principle that fats like vegetable fat or animal fat have a higher power of absorption. This method was primarily used for flowers that give aroma even after harvesting like Jasmine and Tuberose. In this method, flowers are spread over the surface of odourless fat base. The fat base absorbs the perfume emitted from the flowers over a period of 1-3 days or for couple of weeks depending on the flowers used. During this process, the depleted petals are replaced and the process is continued until fat reaches desired situation. At the end of the process, the fat becomes infused with the flower’s fragrance compounds and the oil is extracted with the help of alcohol. The enfleurage process can be done with “hot” or “cold” and the saturated fat is called “enfleurage pomade”. Since it is a very labour intensive and expensive process, it is rarely used today.