1. Purpose of Distillation
- Extract essential oils (agarwood oil / oud) from resin-rich wood.
- Separate volatile aromatic compounds (sesquiterpenes and chromones) from the wood matrix.
- Quality of oil depends on resin content, tree species, and distillation method.
2. Hydro Distillation
Description:
- Wood chips are immersed directly in water and boiled.
- Steam carries volatile compounds → condensed to collect oil.
Process:
- Place chips in a distillation vessel with sufficient water to cover them.
- Heat to boiling; allow vapor to pass through a condenser.
- Collect condensed water + oil mixture; separate oil from hydrosol.
Advantages:
- Simple setup; widely used in traditional operations.
- Suitable for small-scale or artisanal extraction.
Limitations:
- Longer distillation time (24–72 hours).
- Heat can degrade some delicate aromatic compounds.
- Lower oil yield compared to steam or hybrid methods.
3. Steam Distillation
Description:
- Wood chips are not immersed in water.
- Steam is generated separately and passed through the wood to extract oil.
Process:
- Place resinous chips in steam chamber.
- Inject saturated steam through chips at controlled temperature.
- Condense vapor to separate oil and water (hydrosol).
Advantages:
- Preserves delicate aromatic compounds better than hydro distillation.
- More efficient oil extraction.
- Temperature control reduces thermal degradation.
Limitations:
- Requires more sophisticated equipment.
- Risk of incomplete extraction if steam flow is uneven.
4. Hybrid / Hydro-Steam Distillation
Description:
- Combines hydro and steam methods for maximum oil yield and quality.
- Chips are partially immersed in water while steam is injected simultaneously.
Process:
- Place wood chips in hybrid distillation vessel with some water at the base.
- Pass controlled steam through chips while boiling water provides additional heat.
- Condense vapor; separate essential oil and hydrosol.
Advantages:
- Higher oil yield than either method alone.
- Better preservation of aroma compounds.
- Suitable for commercial-scale production.
Limitations:
- Requires careful control of temperature and steam pressure.
- More complex equipment and operation.
5. Factors Affecting Oil Yield and Quality
| Factor | Effect |
|---|---|
| Resin content | Higher resin = higher yield & richer fragrance |
| Chip size | Smaller chips = faster extraction; too small = risk of burning |
| Distillation time | Too short = incomplete extraction; too long = aroma degradation |
| Temperature & pressure | Must balance for maximum yield and minimal thermal damage |
| Water quality | Clean water avoids contamination and odor alteration |
6. Best Practices
- Select resin-rich, graded chips (sinking or super grade) for higher oil quality.
- Control temperature and steam flow to preserve aromatic compounds.
- Avoid direct scorching or high heat to prevent loss of delicate fragrances.
- Separate hydrosol promptly from essential oil for proper storage.
- Store distilled oil in dark, airtight containers at cool temperatures to preserve quality.