Isn’t it wonderful to walk into a room and be surrounded by a subtle fragrance?
Having fresh cut flowers brings the scents of summer into the home for a little while. But imagine if we can capture that perfume and have it easily accessible – anytime.
Fragrances are used extensively in perfumes, soaps, cosmetics, incense and flavoring. Properly harnessed, these fragrances can be powerful aids to health.
Scents are known to elicit positive emotional responses that can trigger physiological reactions. This is why there is such a high demand for better quality fragrances to be used in aromatherapy, massage oils or herbal treatments.
But how do we acquire something so ethereal? How do we capture and preserve these fragrances long after the flower or plant has withered?
How do we capture the volatile oils that make these plants give out their own special scent?
Production of Volatile Oils
Aroma from plants can be found anywhere from the plant itself – whether in the flowers, the fruit, the leaves, the bark or even the roots.
The fragrance is created from aromatic compounds stored in very tiny sacs from the plant. The compounds themselves can be so microscopic that you are literally breathing in the oils that float in the air around the plants.
These oils are considered volatile as they can easily evaporate at normal room temperatures, typically disappearing completely without leaving any trace.
These scents are the ‘essential’ fragrance produced by that particular plant that gives the plant its characteristic fragrance.
Essential oils are so expensive because hundreds of pounds of plant material may be necessary just to squeeze out an ounce or two of volatile oils.
When the aromatic oil is inhaled or absorbed into the body, these plant chemicals can provide many medicinal benefits. Aromas can encourage relaxation, soothe sore muscles, enhance the immune system and purify the body.
Infused Oils vs Volatile Oils
Many essential oils sold on the internet are actually infused oils. The confusion stems from people using the term ‘essential oil’ to mean any scent that has been extracted from plant materials.
A plant can be very aromatic but it will take an incredible amount of that particular plant to extract enough volatile oil from it.
Volatile oils are highly concentrated and far more potent than infused oils. This is why when using volatile oils directly on the skin, these oils should always be in a dilute form such as using them in conjunction with infused oils or with other solutions.
Infusing plant material into other solvents or oils is also the easiest way to yield aromatic oils.
Infusion methods absorb more plant material into the carrier liquid, yielding a much more viscous solution.
Very little volatile oils may be extracted, but larger and heavier plant molecules are captured instead.
Essential oils from macerated infusion are usually not recommended for medicinal or therapeutic use on its own but add benefit when used together with volatile oils.
The infusion process can also be done at home due to its simplicity and the need for fewer raw materials.
The source of plant material will be of utmost importance to ensure that it is pesticide-free and there’s no contamination or infestation.
Fragrances are not only found on flowers and fruit. Some plants store their volatile compounds in their leaves (patchouli, eucalyptus), some within the bark (cinnamon), found in the resin (frankincense, myrrh) or even in the roots (ginger).
Plants are harvested depending on when its levels of volatile essence are at its peak. Flowers are generally gathered when they are about to bloom. Lavender on the other hand, is best harvested when some of its flowers are withering.
The type of plant material gathered, whether from flowers, twigs, leaves or root, will also determine the method of extraction performed. Certain fragrances will not work well with heat or are too delicate for certain processes.
There are three main approaches to obtaining essential oils – extraction, expression and distillation.
We shall be discussing the best methods that use these three approaches.
Oils from the macerated infusion process rely on carrier oils to extract therapeutic properties from plants.
Using this method, more of the actual plant will be absorbed, making this a desirable way of extracting fragrances from delicate flowers or herbs that yield very low amounts of volatile oil.
This method is also ideal for the home as a lower amount of plant material would be needed.
Infused oils will therefore contain beneficial properties from both the carrier oil and the plants that were infused into that oil.
When making infusion oils, dried plant material is preferred as water in the plant means a shorter shelf life for the oil. Moisture may also lead to the oil being contaminated with mold.
When using flowers, careful selection of fresh blooms will help to minimize contamination and prevent the oil from going rancid. It is best to select flowers that are just beginning to bloom as opposed to those in full bloom. This is when the oils will be at its peak.
To begin the process, lightly bruise, chop or crush the plant material to help it release the fragrant oils. Then, immerse them in a glass jar with a carrier oil.
Extra virgin olive oil is preferred as a carrier oil as there is a lower chance of it turning rancid and is relatively inexpensive.
Coconut oil, almond, peanut, safflower, jojoba or grapeseed oil may also be used, with each resulting in an interesting and distinctive blend of aromas.
Allow the botanicals to steep in the oil for a couple of days then carefully strain using a double layer of cheesecloth.
To speed up this process, the infused oil can be gently heated using a crock pot with its lowest setting, stirring periodically to prevent any build up of heat. This mixture can be strained after two hours.
Discard any residue. All residues must be properly removed from the infused oil to prevent it from going rancid.
Repeat the above process as many times as necessary till the fragrance in the oil achieves the desired strength.
Macerated oils should be stored in air-tight glass containers and kept away from heat and moisture.
The perfume industry relies on this method as it significantly increases oil production volume especially when using expensive and delicate plant materials such as rose or jasmine flowers.
This process also produces a finer fragrance as compared to other extraction methods.
Petroleum chemicals such as hexane and alcohol solvents like ethanol can be used to extract the oils. However, these synthetic solvents will leave behind potentially harmful trace in the resulting oil which can lower its therapeutic qualities.
Extracts obtained from these solvents are called concretes. Concretes contain large quantities of wax and resin, making them solid under room temperature.
Concretes will have to be precipitated to remove any debris. What’s left behind is called the absolute.
Absolutes are similar to essential oils as they are highly fragrant, concentrated extracts of the plant.
The chief advantage of procuring extractions of the plant instead of distilling is that a more natural fragrance is achieved because a uniform temperature can be maintained throughout the process.
The disadvantage however, is that residue of the petroleum solvent used would remain in these extracts. This is why oils produced with these solvents are not recommended for therapeutic use but may be used in aromatherapy.
Extraction using supercritical carbon dioxide as a solvent is therefore the preferred method now as it is odorless, colorless, and would revert to its gaseous form once it is released.
With technological advancements, new methods are getting better at extracting volatile oils from plants without altering their sensitive compounds and still being able to retain their natural fragrances.
Cold-press extraction is normally reserved for cooking oil made from seeds or nuts that have a high oil content.
Cooking oils made this way is of a higher quality than those made using heat or chemical extraction. This makes cold-pressed oils ideal for salad dressings and dipping sauces due to their superior flavor.
As cold-pressing does not involve any application of heat, fragrances such as those from citrus fruits that would not hold up well with heat work well with this process. The aroma of citrus essential oil produced would be identical to that of fresh peel.
High levels of heat can cause delicate molecules within volatile oils to break down and degrade. Cold-press techniques help preserve the integrity and potency of oils.
This method is most useful with plant materials that lose their fragrance and beneficial properties when exposed to the heat that is required for steam distillation.
In this method, the whole fruit is placed into a machine that tosses and scarifies the peel to rupture the sacs containing the essential oil.
The pulp mixture will then be put through a centrifuge to filter the fruit remains and other impurities from the liquids.
The solids from the fruit will be disposed, leaving a liquid that is part oil and water. Insoluble oil, which is the volatile oil, is easily separated as it floats.
As large amounts of citrus oil can be harvested from citrus peel, citrus essential oil is therefore cheaper than other essential oils.
This form of distillation has been used to obtain essential oils for hundreds of years and remains one of the best methods to produce therapeutic grade oils.
Cost of production is also considerably lower as there is no necessity to purchase expensive solvents.
Pressurized steam is used to rupture the oil membranes of the plant to release the aromatic compounds.
In this process, the steam must be hot enough to force open the aroma sacs of the plant and yet be gentle enough not to damage the plant or the aroma released. Volatile oils are very sensitive to heat.
Better yield and higher quality of oil is produced by keeping temperatures low and by introducing as little water as possible into the mixture.
When the oils escape and is suffused into the steam, they must then pass through a cooling system which condenses the vapor into a liquid.
From this liquid, the essential oil must be separated from the water. This is easily done as oil, being lighter, will float on the surface.
The water left behind is called a hydrosol, hydrolat, herbal distillate or plant water essence. Rose water or lavender water are examples of hydrosols.
Specialized equipment for distilling greatly influences the quality of oil produced as optimal temperatures and pressures must be achieved.
Distilling equipment include a still to hold the plant matter while it is heated, condenser coils that cool the steam, and a receiving chamber that separates the oil from the water that was condensed.
Constraints to Consistency
The only way to obtain volatile oils is from plant material. This means the plant relied on must first be of the highest quality.
There must also be enough of the raw material to produce enough oil, whether it is done at home or commercially.
Harvesting, gathering and processing practices must also be considered because poor quality control may result in low quality oil or worse, contamination.
Do remember that the efficacy of volatile oils break down with time. This mean there could be some manufacturers who will rely on harmful additives during the bottling and storage process.
Although the shelf life of each product can vary, essential oils should typically be used within a year.
Many essential oils are designed primarily for aroma therapeutic quality and should not be applied topically without some form of dilution. The potential danger of these volatile oils is relative to its purity and to specific chemical components that may react with some users.
The consumer should not be too concerned over which method was used to obtain the volatile oils as different plants and different plant parts require different methods of extraction.
When making a purchase, it is best to count on responsible and reputable manufacturers that list the presence of adulterated additives. Ethical companies would rely on guidelines and standards that ensure the properties of the oil are of the highest quality.