The most important part of sandalwood is heartwood present chiefly in roots of its tree. Sapwood produces lower quality oil. The older the tree the best heartwood we will get from it. For each extraction technique, the quality of the wood determines the quality of the final sandalwood oil. Nowadays, Sandalwood oil is extracted mostly by steam distillation, in this process super heated steam is passed through the powdered wood. The steam then caries the oil locked inside the cellular structure of the wood. After the steam has been cooled we get sandalwood hydrosol and sandalwood oil.
The traditional method to extract sandalwood oil is Hydro-distillation. This process is not so popular these days but it produces good quality of oil. Unlike the stem distillation method steam pass through the powdered wood, then the powder is allowed to soak in water in a hydro-distiller. The water is then heated and the vapor it carries is collected from the top of hydro distiller. The Sandalwood oil is then removed from the top of the hydrosol.
The CO2 extraction method is a latest technique for getting essential oils from plant and its parts. Water or steam is not used in this process. Instead CO2 is used as a solvent. Under high pressure the carbon dioxide or CO2 in short attains a supercritical state and develops a likeness for both gas and liquid. This technique allows sandalwood’s aromatic constituents to be extracted without heat. The carbon dioxide is then removed and processed, refined and filtered. The oil produced by this method has a different feeling and aroma then the oil produced by other two methods discussed above.
The oil we get from this method is more viscous and darker golden in color then steam distilled sandalwood oil. It is not that much sweet smelling if we compare it with steam distilled oil and also it is less spicy.
The difference in aroma from CO2 and steam distilled oil lies in the fact that the heat generated in steam distillation creates some chemical changes in the aromatic constituents of the wood. This further implies that the original chemical constituents are changed to some other chemical and this is the reason why most of the essential oil smells different then the original plant material. The CO2 processed oil smells more like the original plant material because the aromatic chemicals present in plant are not changed as they are distilled using heat.
This does not imply that Sandalwood CO2 oil is better than steam distilled oil. Both type of oil are different and the difference lies in the nature of chemicals which constitute the oil. The CO2 extract aromas are near to the aromas of the original sandalwood plant and that’s why people like CO2 extract oil over steamed distilled oil. Still both techniques are equally important and people love both types of oil. CO2 Sandalwood oil has a very strong and deep aroma. Chemically we get best quality and more quantity from CO2 process and therefore this process has its own importance in conserving the precious sandalwood tree.