Essential Oil Classification and Extractions

The Power and Potential of Plants

Essential Oils for Health, Wellness, and Vitality

Essential oils are highly concentrated plant extracts that capture the natural essence, aroma, and therapeutic properties of the plants they are derived from. Used for centuries and across various ethnobotanical traditions, these oils offer a direct connection to the wisdom of nature.

Essential Oils in Chinese Medicine

In Classical and Traditional Chinese Medicine, essential oils are believed to carry the plant’s Jīng (精) and Yuán Qì (原气)—its intrinsic vitality. These essences interact with the body’s energetic systems, influencing all three levels of Qì (气):

Wèi Protective Qì (卫气) – Wèi Qì is the outer layer of energy responsible for defense and immunity.
Yíng Nutritive Qì (营气) – Yíng Qì is the energy that nourishes and supports the body’s internal functions.
Yuán Source Qì (原气) – Yuán Qì is the foundational energy tied to vitality and life force.

Understanding Essential Oil Types

Not all plant extracts are created equal. Essential oils can be grouped into four primary categories: essential oils, absolutes, concretes, and hydrosols. Each type is distinguished by its extraction process, concentration, and intended use.

Category One: Essential Oils

Essential oils, in the traditional sense, are extracted using steam distillation, cold pressing, or CO₂ extraction. These methods yield the volatile, aromatic compounds that make essential oils prized for their therapeutic and aromatic properties. They are widely used in aromatherapy, skincare, and wellness applications.

Examples of Essential Oils

Star Anise Essential Oil (Illicium verum) – Star Anise essential oil is produced through steam distillation.
Eucalyptus Essential Oil (Eucalyptus globulus) – Eucalyptus essential oil is produced through steam distillation.
Black Pepper Essential Oil (Piper nigrum) – Black Pepper essential oil is produced through steam distillation.

Category Two: Absolutes

Unlike essential oils, absolutes are extracted using solvent-based techniques, allowing them to capture delicate fragrance molecules that steam distillation might degrade. As a result, absolutes are more potent and complex in aroma, making them highly valued in perfumery and luxury skincare.

Examples of Absolutes

Rose Absolute (Rosa damascena) – Rose absolute is produced through solvent extraction.
Tobacco Absolute (Nicotiana tabacum) – Tobacco absolute is produced through solvent extraction.

Category Three: Concretes

Concretes are semi-solid, waxy extracts obtained through solvent extraction. Unlike absolutes, they retain both volatile oils and plant waxes, resulting in an ultra-rich, fragrant extract. These are often refined further to create absolutes, though some are used in their raw form for high-end fragrance and cosmetic applications.

Examples of Concretes

Benzoin Resin Concrete (Styrax benzoin) – Benzoin resin concrete is produced through solvent extraction.
Orange Blossom Concrete (Citrus aurantium) – Orange Blossom concrete is produced through solvent extraction.
Chinese Ginseng Concrete (Panax ginseng) – Chinese Ginseng concrete is produced through solvent extraction.
Jasmine Concrete (Jasminum grandiflorum) – Jasmine concrete is produced through solvent extraction.

Category Four: Hydrosols

Hydrosols, also known as floral waters, are the water-based byproducts of steam distillation. While less concentrated than essential oils, they retain many of the plant’s beneficial compounds, making them ideal for skincare, body care, and mild aromatherapy applications.

Examples of Hydrosols

Rose Water (Rosa damascena) – Rose water is a byproduct of steam distillation.
Lavender Water (Lavandula angustifolia) – Lavender water is a byproduct of steam distillation.

Essential Oil Extraction Methods

The method of extraction plays a critical role in the quality, purity, and intended use of an essential oil. Each technique is chosen based on the material used, desired aroma, and therapeutic properties of the final product.

Understanding these techniques allows for more informed use based on personal needs and desired benefits.

Type One: Steam Distillation

The most traditional and widely used method, steam distillation gently releases a plant’s volatile compounds:

Steam passes through the plant material, breaking open oil-bearing glands.
The released vapors are cooled and condensed into liquid form.
The resulting mixture of essential oil and hydrosol is separated.
This method preserves delicate aromatic molecules, making it ideal for extracting oils from flowers, leaves, and stems.

Examples of Steam Distillation Extracts

Eucalyptus Essential Oil (Eucalyptus globulus) – Eucalyptus essential oil is a steam distilled essential oil.
Tea Tree Essential Oil (Melaleuca alternifolia) – Tea Tree essential oil is a steam distilled essential oil.

Type Two: Cold Pressing (Expression)

Used primarily for citrus oils, cold pressing ensures that heat-sensitive compounds remain intact.

The fruit peel is mechanically punctured and pressed, releasing the essential oils.
The oil and juice mixture is spun in a centrifuge to separate the pure essential oil.

Since no heat is involved, the resulting oil retains its bright, fresh aroma and natural complexity.

Examples of Cold Pressing Extracts

Lemon Essential Oil (Citrus limon) – Lemon essential oil is a cold pressed essential oil.
Orange Essential Oil (Citrus sinensis) – Orange essential oil is a cold pressed essential oil.

Type Three: Solvent Extraction

This method is used for delicate flowers and resins that would degrade under steam distillation.

Plant material is placed in a solvent, such as ethanol or hexane, which dissolves the aromatic compounds.
The solvent is removed, leaving behind a highly concentrated extract.

Further refinement creates absolutes, which are richer and more complex in aroma than steam-distilled oils.

Examples of Solvent Extraction Extracts

Rose Absolute (Rosa damascena) – Rose absolute is a solvent extracted essential oil.
Jasmine Absolute (Jasminum grandiflorum) – Jasmine absolute is a solvent extracted essential oil.

Type Four: Supercritical CO₂ Extraction

A modern, solvent-free method that yields exceptionally pure and potent oils.

Carbon dioxide (CO₂) is pressurized into a supercritical state, where it acts as both a liquid and a gas.
This supercritical CO₂ dissolves the essential oil from the plant material without heat damage.
Once the extraction is complete, the CO₂ evaporates, leaving behind a residue-free, highly concentrated oil.

This technique is ideal for temperature-sensitive botanicals and preserves delicate aromatic compounds.

Examples of Supercritical (CO2) Extraction Extracts

Ginger Essential Oil (Zingiber officinale) – Ginger essential oil is asupercritical CO₂ extracted essential oil.
Clove Essential Oil (Syzygium aromaticum) – Clove essential oil is asupercritical CO₂ extracted essential oil.

Type Five: Enfleurage

One of the oldest and most labor-intensive extraction methods, enfleurage is used for flowers that release their fragrance slowly.

Fresh petals are laid on glass plates coated with a layer of fat, which absorbs the essential oils over days or weeks.
The fat is then washed with alcohol to extract the oil, producing a highly delicate and true-to-nature essence.

Though rarely used today due to its labor-intensive nature, enfleurage remains the best method for preserving fragile floral notes.

Examples of Enfleurage Extracts

Tuberose Essential Oil (Polianthes tuberosa) – Tuberose essential oil is an enfleurage extracted essential oil.
Gardenia Essential Oil (Gardenia jasminoides) – Gardenia essential oil is an enfleurage extracted essential oil.