Essential Oil Extraction Methods: How Aromatics Are Captured

The method used to extract essential oils from plants significantly affects the final product's chemistry, aroma, therapeutic properties, and safety profile. Understanding extraction methods helps you make informed purchasing decisions, interpret product labels, and appreciate the craft behind quality essential oils.

This guide explains the major extraction methods, their advantages and limitations, and how extraction choice affects the oils you use.

Why Extraction Methods Matter

Impact on Quality

Extraction affects:

• Which compounds are captured
• Chemical composition
• Aroma profile
• Therapeutic properties
• Purity and quality
• Price and availability

Choosing the Right Product

When selecting oils:

• Know what extraction method was used
• Understand implications for your purpose
• Match extraction to application
• Consider quality and authenticity

Steam Distillation

The Most Common Method

Steam distillation produces the majority of essential oils worldwide and is considered the traditional standard method.

How It Works

The process:

1. Plant material loaded into still
2. Steam introduced or generated
3. Heat releases volatile compounds
4. Steam carries aromatic molecules
5. Steam + aromatics pass through condenser
6. Condensate separates into essential oil and hydrosol
7. Oil collected from surface

Key equipment:

• Distillation still (alembic)
• Heat source
• Condenser (cooling coils)
• Separator (Florentine flask)
• Collection vessels

Types of Steam Distillation

Direct steam distillation:

• Steam injected into plant material
• Most common commercial method
• Good for robust plant materials
• Efficient extraction

Water distillation:

• Plant material submerged in water
• Water heated to create steam
• Gentler process
• Used for delicate materials

Hydro-diffusion:

• Steam applied from above
• Percolates down through plant material
• Shorter processing time
• Good for certain plant types

Advantages of Steam Distillation

• Produces true essential oils
• Well-established, traditional method
• Relatively cost-effective
• Captures most volatile compounds
• Produces hydrosol byproduct
• Widely accepted in aromatherapy

Limitations

• High heat may alter some compounds
• Some delicate aromatics may be lost
• Not suitable for all plant materials
• Yield can be low for some plants
• Quality depends on distiller skill

Common Steam-Distilled Oils

• Lavender
• Peppermint
• Eucalyptus
• Tea tree
• Rosemary
• Frankincense
• Most floral, leaf, and wood oils

Cold Pressing (Expression)

For Citrus Oils

Cold pressing is the traditional method for extracting oils from citrus peel.

How It Works

The process:

1. Whole fruit or peel collected
2. Mechanical pressing releases oil
3. Oil collected from punctured oil glands
4. Centrifugation separates oil from juice/water
5. Oil filtered and collected

Historical method:

• Hand-pressed using sponges
• Very labor-intensive
• Still used for some specialty products

Modern method:

• Mechanical processing
• High-speed centrifugation
• More efficient extraction
• Consistent quality

Advantages of Cold Pressing

• No heat damage to delicate compounds
• Captures natural aroma profile
• Retains heat-sensitive constituents
• Traditional, authentic method
• Generally good yields from citrus

Limitations

• Only works for citrus peel
• Contains non-volatile components
• Shorter shelf life due to these components
• Phototoxic compounds retained (bergapten, etc.)
• Fruit waxes and color present

Cold-Pressed Oils

• Sweet orange
• Lemon
• Lime
• Grapefruit
• Bergamot
• Tangerine
• Mandarin

Steam-Distilled Citrus Oils

Note: Some citrus oils are also available steam-distilled.

Differences:

• Distilled versions lack furanocoumarins (no phototoxicity)
• Aroma slightly different (less bright)
• Longer shelf life
• Different therapeutic profile

CO2 Extraction

Supercritical Fluid Extraction

CO2 extraction uses pressurized carbon dioxide to extract aromatic compounds, producing "CO2 extracts" rather than traditional essential oils.

How It Works

The process:

1. CO2 pressurized until supercritical (liquid-like density, gas-like diffusion)
2. Supercritical CO2 passed through plant material
3. CO2 dissolves aromatic compounds
4. Pressure released, CO2 returns to gas
5. CO2 evaporates, leaving extract
6. No solvent residue remains

Types of CO2 Extracts

Select extracts:

• Lower pressure/temperature
• Lighter, more volatile
• More similar to essential oils
• Popular in aromatherapy

Total extracts:

• Higher pressure
• Captures more compounds (waxes, pigments, heavier molecules)
• Thicker consistency
• Closer to complete plant representation

Advantages of CO2 Extraction

• Low temperature preserves delicate compounds
• No solvent residue
• Captures compounds distillation misses
• Produces fuller aromatic profile
• Often closer to living plant scent
• Can extract temperature-sensitive materials

Limitations

• Expensive equipment
• Higher product cost
• Not traditional essential oils
• Less historical use data
• May contain compounds not in distilled oils
• Not all practitioners accept them

Common CO2 Extracts

• Frankincense (captures boswellic acids)
• German chamomile
• Calendula
• Vanilla
• Ginger
• Rose
• Coffee
• Turmeric

CO2 vs. Distilled

Frankincense example:

• Steam-distilled: Volatile terpenes only
• CO2 extract: Also contains boswellic acids (therapeutic but non-volatile)
• Different therapeutic profiles
• Both have value

Solvent Extraction

For Delicate Florals

Solvent extraction captures aromatics that can't withstand heat, producing concretes and absolutes.

The Process

Creating concretes:

1. Plant material treated with solvent (hexane typically)
2. Solvent dissolves aromatic compounds
3. Solvent evaporated under vacuum
4. Waxy solid remains (concrete)

Creating absolutes:

1. Concrete treated with ethanol
2. Ethanol dissolves aromatic compounds
3. Waxes filtered out
4. Ethanol evaporated
5. Absolute remains

Understanding Absolutes

What they are:

• Highly concentrated aromatic substances
• Contain compounds essential oils don't
• Closer to natural flower scent
• May contain trace solvent residue

Common absolutes:

• Rose absolute
• Jasmine absolute
• Tuberose
• Mimosa
• Honeysuckle
• Carnation

Advantages

• Captures heat-sensitive compounds
• Fuller aromatic profile
• Reproduces natural scent well
• Only method for some flowers
• Higher yield than distillation for some plants

Limitations

• Possible trace solvent residue
• More expensive
• Not considered "essential oils"
• Some aromatherapists avoid due to residue concerns
• Not suitable for all therapeutic applications

Enfleurage

Historical Method

Enfleurage is a traditional, labor-intensive method largely replaced by solvent extraction but still used for specialty products.

How It Works

Cold enfleurage:

1. Glass plates coated with odorless fat
2. Fresh flowers pressed into fat
3. Fat absorbs aromatic compounds
4. Flowers replaced daily for weeks
5. Saturated fat (pomade) collected
6. Pomade washed with alcohol
7. Alcohol evaporated, leaving absolute

Hot enfleurage:

• Fat heated with plant material
• Faster but less suitable for delicate flowers

Current Use

• Rarely practiced commercially
• Some artisan producers still use
• Educational demonstrations
• Heritage production
• Premium specialty products

Enfleurage Products

• Historically: Jasmine, tuberose, violet
• Now: Rare specialty products
• Very expensive when authentic

Hydrosols: Distillation Byproduct

What Hydrosols Are

Also called:

• Floral waters
• Hydrolats
• Aromatic waters

Definition: Water portion from steam distillation, containing water-soluble aromatic compounds and traces of essential oil.

How They're Made

During distillation:

• Steam carries both oil and water-soluble compounds
• Condensate contains both
• Oil floats on top (mostly)
• Water below retains water-soluble compounds
• This water is the hydrosol

Hydrosol Characteristics

• Much gentler than essential oils
• Water-soluble compounds dominate
• Some oil compounds dispersed
• Different therapeutic profile than oil
• Safe for more direct application
• pH balanced for skin

Common Hydrosols

• Rose hydrosol (Rosa damascena)
• Lavender hydrosol
• Neroli hydrosol
• Chamomile hydrosol
• Witch hazel (technically not same process)

Comparing Extraction Methods

Method Selection by Plant

Method Comparison Chart

*May contain trace solvent

Quality Considerations

Signs of Quality Related to Extraction

Look for:

• Clear extraction method stated
• Single extraction (not blended methods)
• Appropriate method for the plant
• Temperature/pressure information when relevant
• Batch-specific information

Questions to ask:

• What extraction method was used?
• What was the distillation time?
• What temperature was used?
• Is this a first distillation?
• Are there any additives?

First vs. Complete Distillation

First distillation:

• Initial portion of distillation
• Often highest quality aromatic compounds
• Premium product

Complete distillation:

• Full distillation including later compounds
• More complete therapeutic profile
• Standard for most oils

Rectified/redistilled:

• Distilled more than once
• Removes certain compounds
• May alter therapeutic value

Frequently Asked Questions

What's the best extraction method? There's no single "best" method—each serves different purposes. Steam distillation is standard for most therapeutic use, but CO2 and other methods have specific advantages.

Are CO2 extracts essential oils? Technically no—the term "essential oil" traditionally refers to steam-distilled or expressed products. CO2 extracts are aromatherapeutic products with similar applications.

Why are some oils so expensive? Extraction yield varies enormously. Rose requires thousands of pounds of petals for one pound of oil. Labor-intensive methods also increase cost.

Do absolutes contain harmful solvents? Quality absolutes should have minimal residue (typically less than 10ppm). However, some practitioners prefer to avoid them for therapeutic use due to this concern.

Can I tell extraction method from the oil itself? Sometimes—cold-pressed citrus has different character than distilled. CO2 extracts often smell "closer to the plant." But you generally need to rely on supplier information.

What about "therapeutic grade" claims? This is a marketing term, not an industry standard. Focus on extraction method, testing data, and supplier reputation rather than marketing claims.

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Last updated: December 2025. Extraction methods continue to evolve. New technologies may offer additional options in the future.