Essential Oil Classification and Extractions

The Power and Potential of Essential Oils for Health and Wellness

Essential oils are concentrated plant extracts that retain the natural smell, flavor, and 'essence' of their source. When used phytotherapeutically, essential oils are considered to contain the Jīng (精) and the Yuán Qì (原气) of the plant, encapsulating its very life force and working on a similar level in the body. In the context of Chinese medicine, essential oils influence all three levels of Qì: Wèi Protective Qì (卫气), Yíng Nutritive Qì (营气), and Yuán Source Qì (原气).

The Four Major Categories of Essential Oils

Essential oils can be broadly categorized into four subcategories: essential oils, absolutes, concretes, and hydrosols. The extraction method and botanical material used significantly influence the properties and effectiveness of these oils. The main methods of extraction are steam distillation, cold pressing, solvent extraction, supercritical CO2 extraction, and enfleurage.

Understanding these different categories and extraction methods empowers the educated selection and therapeutic use of these highly concentrated plant extracts.

Essential Oils

These are directly obtained through methods like steam distillation, cold pressing, and CO2 extraction. Typically pure, these oils are used in aromatherapy and other practices.

Examples of Essential Oils

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

Absolutes

Highly concentrated aromatic oils typically extracted through solvent extraction, absolutes are more viscous and intensely aromatic than essential oils and are commonly used in the perfumery and cosmetics industries. Delicate flowers like jasmine and rose are often extracted as absolutes.

Examples of Absolutes

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

Concretes

A semi-solid concentrate obtained through solvent extraction, concretes are primarily used as a source for absolutes. They contain both the waxes and the oils from the plant, making them highly fragrant but not suitable for direct skin application.

Examples of Concretes

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

Hydrosols

Also known as floral waters, hydrosols are the water-based solutions left behind after steam distillation. While not as concentrated as essential oils, hydrosols still possess many therapeutic properties and are often used in skincare and aromatherapy.

Examples of Hydrosols

Rose Water (Rosa damascena): Obtained as a byproduct of steam distillation.
Lavender Water (Lavandula angustifolia): Obtained as a byproduct of steam distillation.

Each extraction method and essential oil type has specific uses and benefits, often determined by the chemical makeup of the source plants and the desired characteristics of the final product. Understanding these methods helps in choosing the right essential oil for specific health benefits and applications.

Essential Oil Extraction Methods

Steam Distillation

This is the most common and traditional method for extracting essential oils. In steam distillation, steam passes through plant material in a still, vaporizing the plant's volatile compounds. These vapors then condense back into liquid upon cooling and are collected in a receiving vessel. This method is ideally suited for extracting oils from flowers, leaves, and stems due to its effectiveness in preserving the integrity of the essential oils.

Examples of Steam Distillation Extracts

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

Cold Pressing

Also known as expression or mechanical pressing, this method is primarily utilized for citrus peels. It involves mechanically squeezing the plant material to extract the oils without the application of heat, thus preserving the oil’s fresh, zesty aroma and delicate compounds.

Examples of Cold Pressing Extracts

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

Solvent Extraction

This method is used when the aromatic compounds are too delicate or too tightly bound in the plant to be efficiently released by steam distillation. Solvent extraction involves using chemicals like ethanol (alcohol) to dissolve the plant material and release the essential oils. The solution is then processed to remove the solvent, resulting in a highly concentrated oil.

Examples of Solvent Extraction Extracts

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

Supercritical CO2 Extraction

Utilizing carbon dioxide pressurized into a supercritical state (neither gas nor liquid), this method acts as a solvent to dissolve the plant material and release the essential oils. After extraction, the CO2 is allowed to return to its gaseous state, leaving no residue and producing a very pure oil.

Examples of Supercritical CO2 Extraction Extracts

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

Enfleurage

One of the oldest extraction methods, enfleurage is traditionally used with delicate flower petals. Petals are placed on glass plates coated with a thin layer of fat, which absorbs the essential oils. The oils are then extracted from the fat using alcohol.

Examples of Enfleurage Extracts

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