1. Introduction
Volatile oils, also known as essential oils, are isolated from plant materials to capture their aromatic and therapeutic properties. The isolation process involves various methods, with steam distillation being the most common.
2. Steam Distillation
Principle: Pass steam through plant material to cause the evaporation of volatile oils. Condense the steam-oil mixture and separate the essential oil.
Apparatus: The distillation apparatus includes a still, condenser, and collection vessel.
Examples: Widely used for oils from flowers (e.g., lavender), leaves (e.g., peppermint), and other plant parts.
3. Cold Pressing
Principle: Apply mechanical pressure to plant parts, particularly effective for citrus peels, to release essential oils.
Apparatus: Hydraulic or screw presses are used.
Examples: This method commonly extracts citrus oils like orange and lemon.
4. Solvent Extraction
Principle: Nonpolar solvents (e.g., hexane) dissolve essential oils from plant material.
Process: The solvent is evaporated, leaving behind the essential oil.
Applications: Suitable for delicate flowers (e.g., jasmine) where heat from steam distillation can alter the fragrance.
5. Expression
Principle: Mechanically press or squeeze essential oils out from plant materials.
Process: This method is suitable for citrus peels and is often used interchangeably with cold pressing.
6. Enfleurage
Principle: Place petals on a layer of fat to absorb essential oils, and later dissolve them in alcohol to extract the oil.
Application: Used for delicate flowers like jasmine and tuberose.
7. Hydrodistillation
Principle: Use water instead of steam to extract essential oils, similar to steam distillation.
Application: Use it for certain plant materials that direct steam may damage.
8. Headspace Extraction
Principle: Extract volatile compounds from the headspace above the plant material.
Applications: Suitable for flowers and aromatic plant parts.
9. Challenges in Isolation
Varying Composition: The chemical composition of essential oils can vary based on plant species, growth conditions, and extraction methods.
Heat Sensitivity: Some volatile oils are sensitive to heat, affecting their quality.
10. Quality Control
Analysis: For quality control to ensure the purity and composition of the extracted essential oils, practitioners commonly use gas chromatography and mass spectrometry.
