Essential Oil Production: A Guide to Steam Distillation, Absolutes, and CO2s

 Essential Oil Production: A Guide to Steam Distillation, Absolutes, and CO2s

The 'High Tech' Fusion of Aromatherapy

Aromatherapy is seeing a surge in the use of new essential oil extraction processes, which are opening up a world of oils that were previously unavailable. The aromatherapy enthusiast would do well to educate themselves on the new terms "CO2" and "SCO2" in addition to the more familiar ones such as "steam," "hydro," "absolutes," and "cold pressing" when it comes to essential oil choosing. Is there an optimal procedure? Which one yields an oil with more therapeutic aroma or one with a more pleasant aroma? Essential oil production is both a science and an art, just like winemaking. Both the distiller's level of expertise and the product's intended use significantly impact the value of more modern processing techniques. The production of essential oils suitable for aromatherapy requires the use of each of these methods.

Dehydration with Steam and Water

The majority of essential oils are extracted by steam distillation, which entails passing steam into a chamber containing the plant material. Essential oil is released when tiny sacs containing it burst due to the steam. Once the steam has taken the oil out of the chamber, it is reformed into water in a chilled condenser. (Analogous to this process, hydro-distillation involves boiling the plant material and collecting and condensing the steam that forms). Next, the oil and water are separated. The water, which is called a "hydrosol," can be kept as it contains some of the plant juice. One example is rose hydrosol, which has a pleasant flowery scent in addition to being mildly antibacterial and calming.

The end result of an essential oil's steam distillation depends on a lot of things. Factors like as temperature, pressure, time, and the caliber of the distillation apparatus are more crucial than the plant material itself. An essential oil's medicinal qualities and pleasant aroma are the result of the complicated chemical reactions that occur in its numerous (and often hundreds) constituent molecules. The structures of some of these molecules are quite fragile and can be damaged or even destroyed by harmful environmental factors. So, most oils are best "cooked" for an extended period of time, much like a well-prepared dish.

If the extraction chamber gets too hot, it will change or destroy some of the oil's components. Pressure within the chamber follows the same pattern. As an example, temperatures exceeding 245 degrees Fahrenheit and pressures over three pounds per square inch (3 psi) are not recommended for processing lavender essential oil. The medicinal benefits of the oil are diminished and the aroma becomes more "harsh" and chemical-smelling at higher temperatures and pressures. As some components of the oil are released more rapidly than others, it is necessary to let the extraction phase to continue for a specific duration in order to flush all of the oil's components from the plant.

Even though aggressive processing has its downsides, it is commonly employed to quickly generate huge quantities of oil by using high temperatures and pressures. Essential oils for aromatherapy are a rare exception to the rule; most of the time, these oils find their way into the cosmetics and processed food industries. You can tell the difference when you compare the scents side by side, and these oils will be cheaper, but they won't have much of a therapeutic impact.

Unchanging truths

Steam distillation isn't the best method for some plants, especially flowers. Because of their fragility or because water does not fully extract their therapeutic essences and aroma, some plants are not suitable for use in baths. Despite not being "essential" oils per such, these 'absolutes' will nonetheless have medicinal uses. The oils of certain delicate flowers, like jasmine and rose, are often sold in "absolute" form.

A 'concrete,' a semi-solid blend of about half wax and half volatile oil, is extracted from the plant material using hydrocarbon solvents during the preparation of an absolute first. Due to the wax's low solubility in ethyl alcohol—the same alcohol found in beer, wine, etc.—the concrete undergoes further processing. The plant oil's volatile components separate into the alcohol, which is then extracted. Following careful evaporation, a virtually pure plant extract is obtained; however, occasionally as little as 2% ethyl alcohol may remain, depending on the method used. Despite the fact that absolutes are extracted using solvents, they can nevertheless have very rich and deep fragrances.

Carbon dioxide with sulphur dioxide Gas

Lastly, we have the cutting-edge methods that utilize carbon dioxide and supercritical CO2 extraction. In both processes, carbon dioxide acts as a "solvent" to extract the essential oil from the plant material. Carbon dioxide is cooled to a temperature of 35–55 degrees Fahrenheit and then pumped through the plant material at a pressure of approximately 1000 psi in the lower pressure CO2 extraction process. Under these circumstances, the carbon dioxide has essentially turned into a liquid. The process of supercritical CO2 extraction (SCO2) entails heating carbon dioxide to 87 degrees Fahrenheit and then pumping it through plant material at a pressure of around 8,000 psi. In this state, the carbon dioxide is equivalent to a "dense fog" or vapor. When the pressure is released in either procedure, the gaseous carbon dioxide is released, leaving behind the essential oil.

Some benefits of these carbon dioxide methods are: The end product is very pure, and no solvent residues are left behind, much like in steam distillation. Similar to solvent extraction, neither the plant material nor the essential oil undergo any thermal alteration during this process. When compared to the plant's original condition, the oil that is extracted is spot on. Because most plants have a poor oil yield—for example, one ton of rose petals generates less than one pound of oil—and because the CO2 processes create the most oil per amount of plant, they are also the most efficient. This contributes to the high cost of essential oils. With CO2 extraction, less of the valuable plant is required to make the same amount of oil, which is especially essential when dealing with endangered or uncommon plant species like Indian Sandalwood.

Pressing in Cold Conditions

Lastly, there's the process of "cold pressing" citrus oils—orange, lemon, bergamot, and similar oils—from their respective fruit peels. The oil is extracted by pressing the rind at a temperature of approximately 120 degrees Fahrenheit. These citrus oils keep their vibrant, invigorating scents, similar to that of tasting a deliciously ripe fruit, almost unchanged from their original form.

Pick the Right Approach!

Despite their apparent benefits, CO2s aren't always the route to go when faced with a certain challenge. Even if they produce more, they are still the most costly. Steam distillation of certain plants can occasionally yield oils with a more pleasant aroma, which is one manner in which the final product differs slightly from another method of production. For instance, it appears that patchouli oil gains a little warmer and richer quality when steam distilled. Steam distillation is a very successful method for producing many additional essential oils, and it requires very little processing from the plants themselves. Oils extracted from different plant species actually seem to be more "full" after CO2 processing; for instance, the aroma of frankincense and other "spice" oils is enhanced. With any luck, this means it has better therapeutic effects.

Making aromatherapy-grade essential oils is a skill that takes a lot of practice. A truly great oil requires the labor of an artisanal farmer at every stage, from planting and picking to refining the distillation process. Expertise and practice are much more important than specific extraction methods when it comes to producing high-quality essential oils. But there are good reasons to choose one distillation method over another; for example, some plants can only be processed in a certain way to get fine oil, and there may be only one way to make the oil required for a certain use. Your nose is the ultimate judge of which oil is most suited to your needs, as is typical in aromatherapy.

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