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 encapsulate the natural aroma, flavor, and essence of their botanical source. When utilized phytotherapeutically, these oils are believed to carry the Jīng (精) and Yuán Qì (原气) of the plant—its intrinsic life force—interacting with the human body on an energetic level.

In the context of Classical Chinese Medicine, essential oils are understood to influence all three levels of Qì:

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

The Four Major Categories of Essential Oils

Essential oils can be broadly categorized into four primary types: essential oils, absolutes, concretes, and hydrosols. The method of extraction and the specific botanical material used play a critical role in determining the properties and applications of each type. Common extraction methods include steam distillation, cold pressing, solvent extraction, supercritical CO2 extraction, and enfleurage.

Understanding these categories and extraction techniques equips us with the knowledge to make informed choices and use these highly concentrated plant extracts therapeutically and with purpose and intention.

Essential Oils

These oils are directly obtained through methods such as steam distillation, cold pressing, or CO2 extraction. They are typically pure and widely used in aromatherapy and other wellness practices.

Examples of Essential Oils

Star Anise Essential Oil (Illicium verum): Produced via steam distillation.
Eucalyptus Essential Oil (Eucalyptus globulus): Produced via steam distillation.
Black Pepper Essential Oil (Piper nigrum): Produced via supercritical CO2 extraction.

Absolutes

Absolutes are highly concentrated aromatic oils obtained through solvent extraction. They are more viscous and intensely fragrant than essential oils, making them ideal for use in perfumery and cosmetics. Delicate flowers like jasmine and rose are commonly processed into absolutes.

Examples of Absolutes

Rose Absolute (Rosa damascena): Produced via solvent extraction.
Tobacco Absolute (Nicotiana tabacum): Produced via solvent extraction.

Concretes

Concretes are semi-solid aromatic concentrates obtained through solvent extraction. They contain both waxes and oils from the plant, resulting in a highly fragrant product. While not suitable for direct skin application, they are often processed further to produce absolutes.

Examples of Concretes

Benzoin Resin Concrete (Styrax benzoin): Produced via solvent extraction.
Orange Blossom Concrete (Citrus aurantium): Produced via solvent extraction.
Chinese Ginseng Concrete (Panax ginseng): Produced via solvent extraction.
Jasmine Concrete (Jasminum grandiflorum): Produced via solvent extraction.

Hydrosols

Hydrosols, also known as floral waters, are the water-based byproducts of steam distillation. While less concentrated than essential oils, hydrosols retain many of the plant's therapeutic properties and are often used in skincare and aromatherapy.

Examples of Hydrosols

Rose Water (Rosa damascena): A byproduct of steam distillation.
Lavender Water (Lavandula angustifolia): A byproduct of steam distillation.

Each extraction method and essential oil category serves distinct purposes and offers unique benefits, influenced by the chemical composition of the plant and the desired attributes of the final product. Familiarity with these methods ensures the selection of the most appropriate type for specific health and wellness applications.

Essential Oil Extraction Methods

The method of extraction plays a critical role in determining the quality, purity, and intended use of essential oils. Each technique is tailored to the nature of the plant material and the desired characteristics of the oil. Below are the primary methods used in the extraction process, along with their unique advantages and applications.

Steam Distillation

Steam distillation is the most traditional and widely used method for extracting essential oils. In this process, steam passes through plant material within a still, vaporizing the plant’s volatile compounds. These vapors condense into a liquid upon cooling and are collected in a receiving vessel. Steam distillation is particularly effective for preserving the integrity of oils from flowers, leaves, and stems.

Examples of Steam Distillation Extracts

Eucalyptus Essential Oil (Eucalyptus globulus): Essential oil.
Tea Tree Essential Oil (Melaleuca alternifolia): Essential oil.

Cold Pressing

Also referred to as expression or mechanical pressing, this method is predominantly used for citrus peels. It involves mechanically squeezing the plant material to release the oils without applying heat, ensuring the retention of the oil’s fresh, zesty aroma and delicate compounds.

Examples of Cold Pressing Extracts

Lemon Essential Oil (Citrus limon): Essential oil.
Orange Essential Oil (Citrus sinensis): Essential oil.

Solvent Extraction

This method is used when aromatic compounds are too delicate or tightly bound to the plant material to be efficiently released by steam distillation. Solvent extraction involves using chemicals, such as ethanol, to dissolve the plant material and extract the essential oils. The solvent is then removed, resulting in a highly concentrated aromatic oil.

Examples of Solvent Extraction Extracts

Rose Absolute (Rosa damascena): Absolute.
Jasmine Absolute (Jasminum grandiflorum): Absolute.

Supercritical CO2 Extraction

This advanced method employs carbon dioxide, pressurized into a supercritical state (neither gas nor liquid), to act as a solvent. The CO2 dissolves the plant material, releasing the essential oils. Once the extraction is complete, the CO2 is returned to its gaseous state, leaving behind a pure, residue-free oil.

Examples of Supercritical CO2 Extraction Extracts

Ginger Essential Oil (Zingiber officinale): Essential oil.
Clove Essential Oil (Syzygium aromaticum): Essential oil.

Enfleurage

Enfleurage is one of the oldest and most traditional methods of extraction, especially suited for delicate flower petals. The process involves placing petals on glass plates coated with a layer of fat, which absorbs the essential oils. The fat is then treated with alcohol to extract the oil.

Examples of Enfleurage Extracts

Tuberose Essential Oil (Polianthes tuberosa): Essential oil.
Gardenia Essential Oil (Gardenia jasminoides): Essential oil.

Each extraction method offers distinct benefits, influenced by the chemical composition of the source plant and the desired properties of the final product. Gaining a deeper understanding of these techniques helps in selecting the most suitable oils for specific therapeutic or aromatic applications.