1. Steam Distillation

Mechanism:

  • Steam passes through plant material, causing oil-containing cells to rupture.
  • The mixture of steam and oil vapor is condensed and separated.

Principle:

  • Volatile compounds evaporate with steam and condense into liquid.

2. Hydro Distillation

Mechanism:

  • Plant material is submerged in boiling water.
  • Oil is released into the water vapor, condensed, and separated.

Principle:

  • Heat breaks cell walls, releasing oils which mix with water vapor.


3. Cold Pressing

Mechanism:

  • Physical pressure is applied to extract oils from peels (e.g., citrus fruits).
  • No heat is used, preserving the natural aroma.

Principle:

  • Mechanical force extracts oil without altering its chemical composition.


4. Solvent Extraction

Mechanism:

  • Solvents like hexane dissolve the essential oil from the plant.
  • Solvent is evaporated to leave behind concentrated oil.

Principle:

  • Solubility of oils in organic solvents enables separation.


5. CO₂ Supercritical Fluid Extraction

Mechanism:

  • CO₂ is used at high pressure and low temperature to act as a solvent.
  • When pressure is released, CO₂ evaporates, leaving pure oil.

Principle:

  • Supercritical CO₂ acts like a solvent without leaving residues.


6. Maceration

Mechanism:

  • Plant material is soaked in a carrier oil.
  • Essential oils dissolve into the carrier oil over time.

Principle:

  • Oil-soluble compounds diffuse from plant material into the carrier.

 

7. Enfleurage

Mechanism:

  • Fat or oil absorbs aromatic compounds from flowers.
  • Used primarily for delicate flowers (e.g., jasmine).

Principle:

  • Aromatic molecules dissolve into fats over time.


8. Expression (Scarification)

Mechanism:

  • Used for citrus oils, where peels are punctured and oil is mechanically pressed.
  • Oil is separated from juice by centrifugation.

Principle:

  • Direct physical extraction of oil from plant surfaces.


9. Ultrasound-Assisted Extraction

Mechanism:

  • Ultrasonic waves create cavitation bubbles that disrupt plant cells.
  • Oils are released and collected in a solvent.

Principle:

  • Acoustic cavitation enhances oil release and diffusion.