In this article you will learn all the different ways used for extracting essential oils. By the end you will also have an understanding of why some oils are so much more expensive than others. You will know a little more of what to look out for in oil qualities such as thickness and color. Let’s dive in.
Not all plants can be used for extracting essential oils. The ones that can be used have tiny pouches on the surface of their leaves, flowers, peel or bark that contains the essential oil. When you start peeling an orange and get that spray with its intense orange fragrance, you have broken open the pouches on the surface of the peel. This breaking causes the release of the orange essential oil. In the same way, you release the oils from the rosemary leaf when you rub the leaves between your fingers to produce a smell. There are several methods to produce essential oils by bursting open all these bags to collect the plant’s oil. And, can you believe it, but some of these pouches are found on the hairs on some leaves. Amazing!
Overview of Methods used
The method chosen to produce an essential oil depends entirely on the type of plant material that the oil will be extracted from. Most essential oils are steam distilled, but the oil in some plants and flowers is very delicate and the heat used during steam distillation may destroy them. These delicate oils requires a special method of oil production known as absolute extraction.
The four main methods of production is: steam distillation, the most widely used; expression, a simple method used to extract oil from rinds; absolute extraction or enfleurage, used for very delicate flowers; and CO2 extraction, a new, evolving method that still needs to be explored a bit.
Oilgrow oils are mostly extracted via steam distillation except for the citrus oils which are produced via expression.
Extracting Essential Oils: Steam Distillation
The most popular method is steam distillation. It is a process used for herbs (thyme, basil), roots (vetiver), bark (cinnamon) and resins (frankincense). An ancient method, dating back to around 5000 years, based on the discovery of earthenware stills. Most stills today, are made of stainless steel, copper or glass. The equipment is expensive and yields are low. As example, 10 ton Rose Geranium yields only 20kg oil – that is a 0.02% yield. This is why pure oils are so expensive.
How is it done? A boiler or kettle is used to produce the steam. The distillers places plant materials into a huge pot. Steam travels through the plant material and heats up the volatile oils. Those small pockets of cells burst open to set the oil free to travel out at the top of the pots with the steam. The steam-and-oil mixture then cools down in the condenser (cooling coil) to form liquid again. Since oil and water do not mix, the essential oil normally floats to the top, and is then tapped off. And the oils vary in color and thickness depending on the plant.
Extracting essential oils from Sitrus: Expression
The simplest way to extract an essential oil is to press the plant material and then collect the oil. When the essential oils are found in the outer rind of a fruit, expression is used for extracting essential oils. Citrus fruits, such as grapefruit, sweet orange, lemon, and lime are mechanically pressed to extract their liquid. Once this is done, the watery juice is separated from the essential oil. The oil can be less dense and a definite color tinge is visible. Sweet orange is truly orange, lemon has a light yellow tinge and lime a greenish tinge. This is the least expensive way of extracting essential oils and the yield is much higher. We can offer these oils at much better prices.
Extracting essential oils from flowers: Enfleurage
The fragrance of extremely delicate flowers, such as jasmine and roses, require a method that does not involve steam or water. The result is a highly concentrated oil known as an absolute. In France’s perfumery capital, enfleurage is used. It is a traditional hand extraction method and is a very time consuming process. How is it done? Framed glass plates are covered with lard. They then place delicate flowers on top of the lard. The lard absorbs the fragrant oil after a few days. Alcohol is used to extract the oil and produce the absolute. Modern methods involve blending flowers with a solvent. The solvent is then removed to leave the absolute oil.
Extracting essential oils from flowers: Hydro-distillation
Another method that can also be used is called hydro-distillation. Flowers are mixed with water in a pot, which is heated so that the water and oil is distilled off together. The yields are extremely low. This means the resulting oil/water mixtures have to be re-distilled several times to concentrate the oils. Various fractions of volatile components may be distilled off, changing the oil consistency. This is the case with Ylang Ylang.
Both of these methods are very costly, hence the high prices of such oils. For some flowering species, leaves and stems are steam-distilled together with the flowers. These yields are still small. They are much higher than the ones only flowers are used for, and so the oils are more affordable.
When this method is used it means that the oils are more expensive to make. Many tons of flower petals are needed to make a mere few liters of oil and that adds to the oil’s expensive cost. These oils are also generally a very thick oil. This means that when you purchase an oil of this nature and it is very cheap and watery, it is not a 100% pure oil.
We aim to supply our oils at an affordable cost therefore when we do choose to stock these oils, we make them available in 5ml bottles as well.
CO2 Extraction
Supercritical carbon dioxide (CO2) extraction is a modern method. It uses gas rather than heat. The CO2 is put under pressure to convert it from a gas into a liquid that can be used as a solvent. This solvent is diffused through the plant material to extract its aromatic constituents. CO2 tends to extract additional constituents which has an influence on the aromatic profile and viscosity of the oils. They tend to normally be thicker with heavier or more complex aromatic profiles. It requires more research before it can be used widely. Using CO2 does produce an aroma that is very close to that of the actual plants and might grow in popularity.
The technology is very expensive and cannot be used in rural farming operations, which limits accessibility. It is such a helpful piece of knowledge to have, when you understand how an oil is extracted. It means you have an understanding of how expensive an oil should be, what oil qualities to look out for and how it should be labelled. All these will help you make a great choice when choosing a brand of essential oil to use. Extracting essential oils could be an expensive process and doing it the correct way for different plants are essential.