Author:Shao Hua(Author Affilications:Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences) This article is from popular science expo family science compound (id: kexuedayuan)
When it comes to essential oils, it is estimated that girls (and boys with girlfriends) will not be strangers.
Essential oil aromatherapy (Image: pixabay)
The refining of essential oils can be traced back to ancient Egypt. Cleopatra cleopatra used "sesame oil" skin care, once spent a huge amount of money on the "balm garden" plants to make "sesame oil", she liked to rub jasmine balm when negotiating, "sesame oil" and jasmine balm refers to essential oils.
Stills from Elizabeth Taylor's version of Cleopatra
But why do plants produce essential oils? What chemicals are contained in essential oils? How exactly are essential oils extracted from plant material? The compounder takes you to explore the secrets behind the essential oils today
Essential oil, known as essential oil in English, is a class of secondary metabolites that exist in different parts of plants such as flowers, leaves, stems, roots or fruits, and are mostly volatile aromatic oily liquids at room temperature, mainly composed of terpenes, alcohols, phenols, aldehydes, esters, ketones and other compounds. The compound components contained in each plant essential oil range from as few as a dozen to hundreds of species, and the content of each ingredient is not fixed, which will vary greatly with plant varieties, origin, habitat, growth period, etc.
Among them, the main ingredients of the most famous lavender essential oil are linalool and linaloyl acetate ↓↓:
Lavender essential oil, aroma derived from linalool and linaloyl acetate (Image: veer Gallery)
And the beloved rose essential oil contains more citronellol, geraniol and so on ↓↓:
Bulgaria's Kazanlek Rose Valley, excellent geographical location and climatic environment, make this an excellent source of rose essential oil (Image: cctv9)
These compounds are also important aromatic components of essential oils. The cool odor of essential oils is mostly emitted by the compounds it contains, such as dragon brain, dragon's brain acetate, and eucalyptin. If the content of camphor in essential oils is too high, it will affect the smell of essential oils and reduce the quality of essential oils. These uniquely scented and effective essential oil ingredients are combined in different proportions to form the unique and recognizable aromatic smell of each essential oil.
If you want to know exactly what chemical components are contained in an essential oil, you need to use a gas chromatography-mass spectrometry (gc-ms), using the normal alkane mixture as the standard, calculating and comparing the retention index, and you can know the structure of the compound from the database.
Interestingly, although the chemical composition of various essential oils is significantly different, due to the similar synthesis path, many chemical components can be found in a variety of plant essential oils, such as the common pinene, limonene, dipteroster acetate, terpine, cypressene and so on. The reason why essential oils have the effects of sterilization and anti-inflammatory, sedative and hypnotic, and desalination of scars is also because they contain these biologically active chemical components.
(Image source: provided by the author)
△ The chemical formula structure diagram of the common components of some essential oils, from left to right, are: pinene, limonene, cypressene, dipteroster acetate, γ-terpinolene
Most of the compounds in essential oils are small molecular substances with molecular weights between tens and hundreds and are easily volatile. It is also for this reason that essential oils are generally stored in sealed opaque containers, and the lid should be tightened as soon as possible after each use, and the number of openings should be minimized.
Essential oils are prone to volatilization, so they are usually kept in opaque bottles (Image: pixabay)
In addition to being applied to daily life, essential oils have other development and utilization values. For example, some plant essential oils have the effect of killing insects and weeds, and can be developed into biopesticides. Because essential oils are natural ingredients produced by plants, they can be degraded by microorganisms in nature, avoiding the problem of chemical pesticides polluting the environment, so they are very suitable for the needs of sustainable development.
So, why do plants produce essential oils? Small partners can not be sentimental, plants produce essential oils are definitely not for human use, to give us whitening acne, people are of course from their own interests.
For example, some plants such as flowers produce essential oils in order to attract insects to pollinate; and conifers produce essential oils to avoid pests and inhibit the growth of pathogenic bacteria; and some plants such as the Italian ear of the Asteraceae family, the thorn ear, etc. can produce chemical components that inhibit the growth of other plants, and they secretly release these compounds into the air and pass them to neighboring plants, so that neighbors can grow poorly, so that they can enjoy more valuable resources such as light and nutrients. This is the so-called allelopathy, which is allelopathy in English, and is one of the necessary invasion magic weapons for a variety of exotic plants.
So you see, since plants can't change their position like animals, they have to rack their brains and produce secondary metabolites with various biological activities, and essential oils are just a secondary metabolite with specific physiological and ecological functions that they synthesize.
Although plants produce essential oils that are not for human service, since humans have found such a good treasure, how can they easily let it go.
Human beings have long been using plant essential oils, extraction methods include water vapor distillation, chemical solvent extraction, supercritical fluid extraction, etc., water vapor distillation method is the most common, we see in the market lavender essential oil, Roman chamomile essential oil, rose essential oil are extracted with this method.
A device for large-scale extraction of essential oils from plants (Image source: courtesy of the author)
In fact, the equipment for refining essential oils is not complicated at all, and the principle is very simple. Everyone has seen the steamed bun scene, right? The equipment used to refine the essential oils is a large pot of steamed steamed buns equipped with a condensation system.
For small-scale refining in the lab, we put the cut plant material into a round-bottom flask, add water to the material, and then heat it with an electric heating sleeve, and keep it slightly boiling for 2-4 hours after the water boils. At this time, the volatile components in the plant material will be steamed out with the water vapor. The round bottom flask mouth is connected to the volatile oil collector and the condensing tube, and the steamed water vapor meets condensation upwards, drips in the collector and is collected.
At this time, some components are insoluble in water and the specific gravity is less than water, will float on the surface of the water, forming what we call "essential oil"; the lower layer is water with a large specific gravity, but it is not pure water, which contains a small amount of essential oil components, but also contains complex multi-plant water-soluble compounds, we call it "pure dew".
Equipment for small-scale refining of essential oils in the laboratory (Image source: provided by the author)
The extraction rate of essential oils is not high, generally between a few tenths of a percent and a few percent. Because microorganisms cannot grow in essential oils, their shelf life is very long, and they are said to be able to last for one hundred years. Depending on the chemical composition of the essential oil, the extracted essential oil may appear colorless, light yellow, golden, light green, sky blue, purple and black.
Different colors of essential oils with different chemical compositions (Image: pixabay)
Yes, you read that right, there are indeed black essential oils in this world, and the essential oil of Artemisia annua in Xinjiang, which was extracted by our laboratory (The Phytochemistry Department of the Key Laboratory of Biological Resources and Biogeography of the Xinjiang Institute of Ecology and Geography of the Chinese Academy of Sciences) not long ago, is ink black and inky black, almost like black ink!
Black essential oil of Artemisia centruma extracted from volatile oil extractor (Image source: Courtesy of the author)
The black color is caused by the abundance of sagebrush (The English name azaulene, pronounced yu, homophonous with "healing", is also often called sky blue hydrocarbons) in the essential oil of Artemisia annua in Central Asia. ) and its derivatives. However, the plant itself does not contain catalpa and its derivatives, which are formed by the decarboxylation reaction of matricin (matricin) in the plant as a precursor during distillation.
In some plant essential oils, the content of sagebrush or its derivatives is low, at this time the essential oils show a beautiful sky blue, such as chamomile essential oil, mugwort essential oil, Xinjiang artemisia flower essential oil and so on. It is not only the face value of a variety of essential oils, but also has the functions of anti-inflammatory and mucosal repair, which can be applied to drugs, cosmetics, daily necessities and so on.
So can the little friends refine their own essential oils at home? Of course you can, but only if you're skillful.
The following compounder will briefly describe the steps of extracting essential oils at home for you (this paragraph can also be skipped without reading, anyway, most people will not really do it after reading it~):
First of all, we have to find a heated container in the kitchen, which can be a kettle or a pressure cooker (remove the pressure valve), and then find a plastic hose, and it is better to find a silicone tube that can withstand high temperatures. Connect one end of the hose to the outlet of the kettle or the outlet of the pressure cooker, the other end to the collection bottle (which can be a large spring water bottle), and find a container (such as a large pot) filled with cold water to use as a condenser, and you can begin.
Add the plant material you want to distill in the kettle or pot, such as mint picked in the yard, or buy lavender flowers, add water to submerge, or put it on the cage drawer to steam, heat it to a boil. Immerse the hose in a large pot filled with cool water, and connect the outlet to the collection bottle, so that the essential oil components steam out with the water vapor, condense after passing the cold water, and divide the collection bottle into two layers, the upper layer is the essential oil you refine, and the lower layer is pure dew. Essential oils can be stored for a long time because of their bacteriostatic effect, while pure dew is recommended to be used up within half a year.
(Tips: Please do a good skin test before self-use to make it hypoallergenic.) This product is for personal use only and cannot be sold.
Some foodies must be curious, since they are called "oil", can the essential oil be used to stir-fry or cold mix? It is very tempting to think about it, using rose essential oil to make a cold chicory, using fragrant lavender essential oil to fry a garlic bacon, is it listening to the saliva is about to flow down?
The reality is that although the same fat-soluble chemicals are, essential oils are inedible due to the extremely different composition of edible oils and essential oils. Edible oil is mainly composed of unsaturated fatty acids, with a large molecular weight, which cannot be produced by water vapor distillation, but by pressing. And the essential oil is composed of volatile small molecule compounds such as terpenes, so it can not be eaten Oh, if you force it into the wok, as the temperature rises, the essential oil will gradually volatilize out, you can only hope that the pot is happy to sigh!
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In recent years, the use of essential oils has become more and more popular, and even old mothers know that when soaking their feet, a few drops of lavender essential oil are dropped to soothe fatigue.
In the past, when lavender was mentioned, people thought of Provence in France; and after decades of development, Huocheng County, Ili Prefecture, Xinjiang, China has become a famous "Hometown of Chinese Lavender". Because Huocheng is located at the same latitude as Provence, the climatic conditions and soil environment are similar, which is very suitable for the growth of lavender, and its lavender production accounts for more than 90% of the country.
Lavender in Ili, Xinjiang (Photo: Xi Ruishan)
Every year in the middle of June, Huocheng will usher in the lively lavender festival, the whole county becomes a sea of purple flowers, and the air is filled with sweet smells. The Tianshan Mountains blow snow and purple, and saiwai fang fei wins the jiangnan. Friends can take the opportunity to travel to Xinjiang, and they can also pick up a few bunches of fresh lavender to refine essential oils and pure dew!