Fragrance extraction facts for kids
Fragrance extraction is all about getting wonderful smells from natural stuff like plants. It's how we get the amazing scents used in perfumes, soaps, and even some foods! Think of it as a special way to separate the good-smelling parts from raw materials.
There are different ways to do this, like distillation (using heat), solvent extraction (using liquids), pressing (squeezing), or enfleurage (using fats). What you get at the end can be an essential oil, an absolute, or a concrete. It depends on how much wax is left in the final product.
Sometimes, the way we extract a smell can change it a little. Heat or chemicals might make some of the scent molecules different. This can change how the smell comes across or even make it disappear. Also, not all parts of the smell are always extracted in the same way.
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How to Get Scents: Solvent Extraction
Some plants don't have enough natural oil to be squeezed out, or their delicate scents can be easily ruined by heat. For these, we use special liquids called solvents to pull out the smells.
Using Organic Solvents for Fragrance
Using organic solvents is a very common and important way to get scents for perfumes today. Imagine soaking raw materials in a liquid that can dissolve the good-smelling parts. These liquids, like hexane or dimethyl ether, are called solvents.
When you use organic solvents, you get the fragrant parts along with other oily things like wax and colors. The liquid is then removed using a special vacuum process, so it can be used again. This whole process can take hours or even months! This method is often used for woody plants or for scents from animals. It's also great for smells that are too delicate for heat.
The waxy stuff left behind is called a concrete. It's a mix of essential oil, waxes, and other plant materials that dissolve in oil. The solvent is then taken out at a lower temperature and reused.
Concretes smell great, but they are often thick or even solid at room temperature because of the waxes. To get just the pure scent, another liquid, usually ethyl alcohol, is used. This alcohol only dissolves the good-smelling parts, leaving the waxes behind. The alcohol is then removed by another heating process, leaving behind a pure absolute. Scents from plants like jasmine and rose are often made into absolutes this way.
Because this process uses low temperatures, the absolute often smells very much like the original plant. This is different from methods that use high heat, which can change the scent.
Supercritical CO2 Extraction: A Modern Way to Get Scents
Supercritical fluid extraction is a newer way to get fragrant compounds. It often uses supercritical CO2 (carbon dioxide under high pressure) as the special liquid. When carbon dioxide is put under high pressure and is a bit warmer than room temperature, it becomes a supercritical fluid. (Normally, CO2 goes straight from a solid to a gas, like dry ice!)
This special CO2]] can easily get the oily, good-smelling parts from plants. It's actually the same process used to make decaffeinated coffee!
In this method, high-pressure carbon dioxide gas (up to 100 times normal air pressure) acts as the solvent. Because it uses low heat and a gentle solvent, the scents often smell very much like the original plant. Like other solvent methods, CO2 extraction happens at a low temperature. This means the scents are not changed by heat, so the smell is very true to the original. Since CO2 is a gas at normal air pressure, it leaves no trace in the final product. This means you get the pure absolute right away, without having to deal with a concrete first. The solvents are also easy to remove. The scents made this way are called CO2 extracts.
Ethanol Extraction: Making Tinctures and Absolutes
Ethanol extraction uses ethanol (a type of alcohol) to get fragrant compounds. It can be used directly on dry plant materials or to clean up oils and concretes from other extraction methods. When ethanol is used on dry materials, the result is called a tincture. When it's used to clean oils and concretes, it helps create absolutes.
The impure oils or concretes are mixed with ethanol. Ethanol is good at dissolving the fragrant parts that have changed a bit (like alcohols and aldehydes), leaving behind waxes, fats, and other oily stuff. The alcohol is then evaporated at low pressure, leaving the pure absolute. This absolute might be cleaned even more to remove any last impurities.
Ethanol extraction isn't usually used for fresh plants because fresh plants have a lot of water, which would also get mixed with the ethanol.
Distillation: Heating for Heavenly Scents
Distillation is a common way to get fragrant compounds from plants like orange blossoms and roses. The plant material is heated, and the good-smelling parts turn into a vapor. This vapor is then cooled down and collected as a liquid. The products made by distillation are called essential oils or ottos.
Today, many common essential oils, like lavender, peppermint, and eucalyptus, are made this way. The raw plant material – which can be flowers, leaves, wood, bark, roots, seeds, or peel – is put into a special machine called an alembic over water.
Steam Distillation: Capturing Scents with Steam
Hot steam from boiling water passes through the plant material for about 60 to 105 minutes. This steam pulls out most of the good-smelling parts. The steam then cools down and turns back into a liquid, which contains both water and the fragrant oils. This liquid settles in a special container called a Florentine flask. The fragrant oil floats to the top, making it easy to separate from the water.
The water that's left behind still has some of the fragrant compounds and oils. This scented water is called a hydrosol. Hydrosols like rose water, lavender water, and orange blossom water are sometimes sold for people to use. However, many plant hydrosols don't smell very nice, so they aren't sold.
Most oils are distilled in one go. But some, like Ylang-ylang, take a very long time (22 hours!). Ylang-ylang is distilled in stages, producing different grades of oil.
Dry Distillation: For Smoky, Toasted Scents
Also known as rectification, this method heats the raw materials directly in a still without water. The high heat can cause some of the fragrant compounds to change, creating new smells. This method is used to get scents from fossil amber and fragrant woods like birch tar. It's used when a "burned" or "toasted" smell is wanted.
Fractionation Distillation: Fine-Tuning Fragrances
Using a special column, different parts of the distilled material can be separated. This allows perfumers to remove unpleasant smells or unwanted notes from a material. While it makes the product more expensive, it gives the perfumer more control over the final scent. This process is often done as a second step on material that has already been extracted, rather than on raw plants.
Expression: Squeezing Out Citrus Smells
Expression is a way to get fragrance by pressing, squeezing, or compressing raw materials to collect the essential oils. Today, this method is mostly used for the peels of citrus fruits like oranges and lemons. This is because citrus peels have a lot of oil, making it an affordable way to get their scents. Citrus peel oils are pressed by machines, a process called cold-pressing.
Because citrus fruits have so much oil and are relatively cheap to grow, their oils are less expensive than most other essential oils. For example, pure limonene (a common citrus scent) is an affordable natural solvent. Lemon and sweet orange oils are often by-products of the commercial citrus juice industry.
Expression was used a lot before distillation was discovered, and it's still used in some cultures, like ancient Egypt. The ancient Egyptians would press plant material and then bury it in special unglazed ceramic pots in the desert for months. The water would slowly seep out through the pots, but the larger essential oils would stay inside. The lotus oil found in Tutankhamen's tomb, which still smelled after 3000 years in alabaster jars, was made this way.
Enfleurage: An Old Way to Capture Delicate Scents
Enfleurage is a process where the smell of fragrant materials is soaked up by wax or fat. This scented wax or fat is then often cleaned with alcohol. Enfleurage was commonly used when distillation wasn't possible because some delicate scents would be ruined by high heat. This method is not used much in modern industry today. It's very expensive and there are now more efficient ways to get scents.
