Essential Oil Extraction Methods: The Science Behind The Scent

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We know that essential oils are concentrated liquids that capture the very essence of a plant. But do you know exactly how we get these potent fragrances from leaves, flowers, and other plant parts?

There are multiple essential oil extraction methods, each with its own unique approach. Different methods are used to obtain different extracts, depending on the nature of the botanical used.

Here’s an interesting look into various techniques to extract essential oils from aromatic plants, uncovering the secrets behind their captivating scents and therapeutic properties.

First though, if you’re new to aromatherapy, a quick overview of what are essential oils may help.

Understanding Essential Oils & Their Volatile Nature

To truly understand essential oil extraction, it helps to grasp the essence of what essential oils are. Essential oils are volatile oils that give plants their characteristic odors and are used especially in perfumes and flavorings, and for aromatherapy. The key word here is “volatile,” which refers to the ability of a substance to evaporate easily at normal temperatures.

Essential oils are composed of numerous chemical constituents, each contributing to the oil’s unique aroma and therapeutic properties.

It’s important to note that producing a single bottle of essential oil requires processing a large quantity of plant material, resulting in a highly concentrated and potent essential oil.

Steam Distillation: The Classic Essential Oil Extraction Method

illustration of the steam distillation process used to extract essential oils

Steam distillation is the most widely used method for extracting essential oils. This classic technique involves using hot steam to release the aromatic compounds from the plant material.

Here’s a step-by-step breakdown of the steam distillation process:

1. The plant material, known as the “charge,” is placed in a still. Depending on the plant, the charge may be composed of the flowers, leaves, bark, or roots of the plant.

2. Steam, usually pressurized, is passed through the charge. The pressurized steam ruptures the tiny sacs containing the essential oils, releasing the oil into the steam.

3. The steam, along with the essential oil, rises to the top of the still and enters a condenser, which consists of a long spiral pipe surrounded by cold water. The condenser cools the steam, causing it to condense back into its water form.

4. This liquid mixture separates naturally into two layers: the precious essential oil ( a lighter and non-water soluble layer) and a hydrosol (a floral water such as rosewater).

5. At the end of the condenser, the water and essential oil mixture is collected in a receiver, called the “Florentine flask,” designed with separate outflows for oil and water.

6. Since essential oils are lighter than water, they float above it, allowing the hydrolat or hydrosol (water portion) to be drawn off from the lower outflow of the flask.

7. This continuous separation of oil and water is necessary to prevent the flask from overflowing.
The collected essential oil is then ready for further processing and utilization.

Steam distillation is the preferred essential oil extraction method for its ability to produce high-quality essential oils. This process distills the volatile compounds from the plant parts at temperatures that are much lower than their boiling points. This preserves the natural components so that their characteristics are not diminished or altered during the process.

Popular examples extracted through this method include Lavender, Peppermint, and Tea Tree essential oils.

Cold-Press Essential Oil Extraction Method

whole and cut lemons and a bottle of essential oil

As the name suggests, cold press extraction does not use any form of heat. This is a gentler approach that’s ideal for extracting delicate essential oils from the rinds of citrus fruits.

Cold-press extraction involves these steps:

1. In the cold-press extraction process, whole citrus fruits are placed in a device that mechanically pierces the rinds of the fruit. This ruptures the essential oil sacs, which are located on the underside of the rind.

2. The volatile essential oil, juice, and pigments get released from the sacs and run down the collection center built into the cold-press equipment.

3. The oil and juice extracted and collected still contain solids such as rinds and pulp from the fruit. The extract is centrifuged to separate the liquids from the solids.

4. As oil is lighter than water and juice, it separates and floats to the top, from where it is siphoned off into another receptacle, ready to be bottled.

5. Since no heat is involved, this method helps retain the volatile compounds of the oil, often resulting in a brighter and fresher aroma.

However, cold pressing yields a lower quantity of essential oil compared to steam distillation and is limited to specific plant materials.

Solvent Extraction Of Essential Oils

This essential oil extraction method uses food-grade solvents such as ethanol and hexane to isolate volatile oils from plant material. It is best suited for plant materials that yield low amounts of oil and botanicals that are more delicate and unable to withstand the pressure and distress of steam distillation.

The oils obtained through solvent extraction are not strictly essential oils, they are more accurately referred to as “absolutes.” That’s why you’ll see that these oils are known as Rose Absolut and Jasmine Absolut oils.

Solvent extraction produces oil with a finer fragrance than any type of distillation method.

Here’s a step-by-step breakdown of the solvent extraction process:

1. The flowers are covered with a chemical solvent, which absorbs the essential oil, forming an extract.

2. The extract is then distilled at low pressure to remove the solvent. This is done by reducing the boiling point of the solvent, allowing it to evaporate gently.

3. The concentrated extract, known as “concrete,” is obtained once the solvent is removed.

4. To eliminate unwanted waxes, the concrete is washed and warmed in alcohol, releasing the oil particles.

5. The alcohol mixture is then chilled to separate any remaining waxes. It is then filtered and the alcohol is removed through vacuum distillation.

The final product is an absolute, which retains the true essence of the flower’s aroma.

CO2 Extraction: A Sustainable Essential Oil Extraction Method

Carbon dioxide (CO2) extraction is a relatively recent development in the field of essential oil extraction.

This method works by pressurizing carbon dioxide so it reaches its supercritical state, where it becomes liquid while remaining in a gaseous state. At this point, it is neither a conventional liquid nor a gas. Instead, it exhibits both liquid and gas-like properties.

The CO2 extraction process involves the following steps:

1. Carbon dioxide is pressurized and reaches its supercritical state where it exhibits both liquid and gas-like properties.

2. In this supercritical state, CO2 is pumped into a chamber filled with plant material.

3. Because of its liquid properties in this state, carbon dioxide acts as a solvent, extracting the oils, pigments, and other substances such as resin from the botanicals.

4. The volatile oils dissolve into the liquid CO2 while the resin remains undissolved.

5. The extraction takes place in a sealed chamber to ensure the recovery of the entire oil, including the most volatile and fragile components.

6. Once the extraction is complete, the pressure is released, causing the carbon dioxide to return to its gaseous state while leaving behind the volatile essential oil.

CO2 extraction is known for producing high-quality oils with a unique composition and aroma, distinct from those obtained through steam distillation.

The CO2 essential oil extraction method is hugely popular due to its efficiency, minimal use of solvents, and ability to produce high-quality oils.
The extracts obtained through this method are thicker and more aromatic as compared to oils extracted through some of the other methods.

Enfleurage Essential Oil Extraction Method

Enfleurage is a historical essential oil extraction method that has been used for centuries. It is the preferred technique for capturing the delicate scents of flowers.

Highly purified and odorless vegetable or animal fat, generally lard or tallow, is spread on glass plates that are set in a frame known as a chassis.

There are two types of enfleurage techniques – cold and hot.

The cold enfleurage extraction process involves the following steps:

1. The oil is left to set on the glass plates.

2. Fresh flowers, either whole or only the petals, are placed on top of the set layer, pressed into the fat, and left undisturbed for a while.

3. The time reserved for the flowers to set depends on the plant. Some flowers require only about 1 to 3 days, while others may need a few weeks.

4. During the setting period, the fat absorbs the volatile oils from the flowers and becomes scented.
When all the oils have been extracted from the petals, the depleted petals are replaced with a fresh lot.

5. This process is repeated multiple times until the fat becomes saturated with essential oil, forming a compound known as a “pomade.” The pomade is composed of fat and aromatic oil extracted from the flower.

6. To extract the essential oil from the pomade, the pomade is washed in alcohol which causes it to dissolve. When the alcohol evaporates from this mixture, it leaves behind the “absolute” essential oil.

The fat from the pomade is used in soap-making.

HOT ENFLEURAGE

The hot enfleurage essential oil extraction method is similar to its cold counterpart except for one difference. In the hot enfleurage technique, the fats are heated before placing the plant parts.

Maceration: Home Extraction Method

cut yarrow and carrier oil in two white bowls and another jar containing a mxiture of cut yarrow and essential oils

I want to mention maceration if only because it is often included as one of the essential oil extraction methods. However, you should know that the extract obtained through maceration is technically not an essential oil. It is an infused oil.

Maceration involves using a carrier oil as a solvent to extract the therapeutic ingredients from the plant material.

Note: It extracts the therapeutic ingredients from the botanical. It does not extract the volatile oil, hence the end product cannot be called an essential oil.

In maceration, the plant part is lightly crushed or cut to rupture the cells and oil glands. The crushed botanicals are placed in warm carrier oil and left to steep for a few days to a few weeks.

The carrier oil absorbs the essential oil, and the plant material is strained off.

Fresh plant material can then be added to the warmed carrier oil, and the process is repeated until the oil is concentrated enough.

Maceration is the only method that you can perform at home.

Comparing Extraction Methods: A Comprehensive Overview

To better understand the differences between the various extraction methods, let’s compare them side by side:

Extraction Method Pros Cons

Steam Distillation – Widely Used Method

Preserves the aromatic profile
Suitable for a wide range of plant materials
Longer extraction process
Heat may degrade certain compounds

Expression – Simple & efficient for Citrus Essential Oils

Preserves the fresh aroma
No chemical solvents involved – Limited to citrus fruits
Manual expression method is time-consuming

Solvent Extraction – Extracts Delicate Flower Oils

Retains true floral aroma
Allows extraction of non-volatile compounds
Produces high-quality oils with unique composition and aroma
Preserves delicate compounds – Higher concentration of pesticide residues
Requires specialized equipment

Enfleurage – Captures Delicate Floral Scents

Suitable for fragile flowers – Time-consuming process
Requires large quantities of flowers
Not cost-effective for commercial production

Maceration – Homemade Method

Ready-to-use diluted essential oil
Simple process
Longer extraction time
Diluted concentration of essential oil

The extraction method to obtain any essential oil depends on several factors, including the type of plant material, the desired yield and quality of the oil, and economic considerations. Each method has its own advantages and limitations, making the choice a crucial step for essential oil producers to ensure a potent, pure, and therapeutic essential oil.

Understanding essential oil extraction processes definitely instills a deeper appreciation for the essential oils you use.

Can You Make Essential Oils At Home?

I see a lot of readers asking this question on various forums and wanted to answer it because many people give the wrong advice.

You can make essential oils at home, but you shouldn’t.

The process of extracting essential oils requires precise equipment, techniques, and knowledge to ensure purity and safety. Home extraction can lead to contamination, low yield, or even dangerous substances if not done correctly.

It’s best to purchase essential oils from reputable suppliers who use proper extraction methods and quality control. Plant Therapy is my #1 recommended essential oil brand. Read my Plant Therapy brand review to see why I use oils from this brand.