Essential Oils: Extraction Methods of Essential Oils

Essential Oils and Aromatherapy

 


Essential Oil Extraction Methods

There are several different extraction methods used on plant materials to extract the essential oils from them. The method used will depend on the source material, ease of extraction, and other variables. This page will take an in-depth look at the different extraction methods used to obtain essential oils.

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Extraction Methods of Essential Oils

by Susan Siegenthaler

Essential oils are mixtures of organic compounds such as alcohols, esters, ketones, and aldehydes. There are nearly 1000 naturally occurring mixtures of these compounds. Essential oils have a specific composition with small variations dependent upon climate and soil, methods of cultivation and extraction processes used.

The wild plant is preferred as it yields the most active and most balanced product. Cultivated plants are best raised sympathetically and organically. Synthetic pesticides should not be used as these are often soluble in the plants aromatic substances. Gathering should take place at full maturity and extraction of oils carried out with care.

Essential oils are the quintessence of the plant, with specially evolved qualities which attract pollinating animals, repel parasites, and catalyse chemical reactions.

They are considered to be plant hormones (phyto-hormones) and have biodynamic and ionising potential when used therapeutically. For this reason they should be used with care, in suitably diluted doses - any excess can be harmful to health.

Main methods used are:

The Extraction method used depends on a number of factors:

  1. The ease with which the substances can be removed from the plant material
  2. The type of plant material
  3. The costs involved in extracting the substances

PRESSING:

This method of extraction is used to remove essential oils from the seeds, nuts and rinds of plants, e.g. oranges produce sweet orange oil in the rind, limes, lemons, cloves, jojoba nuts.
Many of our carrier or base oils are extracted by this method.

COLD PRESSED OILS are extracted by the 'Pressing' method. The plant material is bruised, crushed and ground in a 5-roller mill which comprises chilled iron or steel rollers. The plant material is placed under 300 atmospheres pressure for 7 minutes! This amount of pressure does produce heat, but is still considered 'Cold Pressing'.

HOT PRESSING involves pressure of up to 15 tons per square inch, producing a heat of 65 to 150 degrees centigrade. As less oil can be extracted when Cold Pressing methods are used, Cold Pressed oils are more expensive. However, the benefits of cold pressing are that the oils are not badly effected by heat, and are therefore more stable once extracted, and their chemical composition has not be interfered with. There is a great deal of concern in regard to Hot Pressed oils in relation to their possible 'carcinogenic (cancer causing) properties.

The last thing we need to be using as Aromatherapists are oils which may have a detrimental effect upon the health of our patients or ourselves!

ENFLEURAGE:

This method of extraction involves the absorption of the essential oil into a fatty substance. It is usually used to extract essential oils from fairly soft plant materials, e.g.: flowers, buds, petals and so on. In the 'Enfleurage' method the flowers or other plant materials, are spread in a glass dish which contains some type of purified fat.

In less modern times, purified lard was often used for this purpose. The plant material is then Left for 72 hours, and then replaced by fresh plant material at 72 hour intervals. This process is repeated time and time again until the fat medium is 'saturated' with essential oil. The resulting fat is called a POMADE.

This pomade is dissolved in a solvent (often alcohol). The fatty substance itself does not dissolve, but sinks to the bottom of the vessel, while the essential oil is dissolved in the alcohol. The alcohol is then gently heated, and separates into its component parts of hydrogen and oxygen, and the essential oils too are carried on the oxygen molecules, through a glass tubing and deposited into a collecting vessel.

The oxygen and hydrogen gases meanwhile, cool down and form water, which is collected in another collecting vessel. This final separation of the essential oil from the alcohol is a basic distillation method. This method is considered to be the best method for essential oil extraction, and the oils obtained in this way are more concentrated, more stable and are not unduly damaged by the process, Oils like Rose, Jasmine and Neroli are collected in this way.

MACERATION:

Maceration is the process by which the plant material is left to 'soak' in a solvent or oil carrier. This may take days, weeks, or months, depending on the concentration of essential oil desired and of course the plant material from which the essential oil is being extracted. It is a very simple process, and can be used at home to make your own Infused Oils.     

Commercially, when this method is used, a similar distillation process to that described in the Enfleurage method is used to extract the essential oil from the solvent or carrier oil base.

DISTILLATION:

The Distillation method is used where the oils adhere so strongly to the plant material that steam heat must be used to separate them, e.g. as in eucalyptus oil extraction, or where the essential oil content of the plant is so minute that a stronger method of extraction must be used so that all the essential oil content in the plant material can be obtained. In the Distillation process steam is passed over the leaves or flowers and the essential oil evaporates off the plant material with the steam.

As the steam cools down, it turns back into water which is collected in a collecting vessel, and the essential oil settles on top of this. Being lighter than water, the essential oils can be either skimmed off the surface of the water, or can be very easily tapped off.

TAPPING:

This method of extraction is also used to tap maple syrup from maple trees, and rubber from rubber trees. Usually resins and gums are extracted by this method, e.g. Benzoin.

A tap is simply placed into the cambium layer of the tree, and the resin or gum is allowed to run off into a collecting vessel at the foot of the tree. The collected material would then more than likely be purified in some way to remove 'ballast' or unnecessary substances.

SEPARATION BY HEAT:

This is a very ancient extraction method and is still used in countries like India, China, Egypt.

The plant material is placed in a heat proof container, over a water-bath, and heat is then applied to the water bath. The constant low heat causes the plant material to give up its essential oils and resins. As this accumulates in the Bowl, the old plant material is replaced by new and so the process goes on until the desired quantity of oil or resin is obtained. The Separation by Heat method is used to extract Myrrh gum and Turpentine oil, for example,

DISSOLVING:

In this process, some solvent is used in which the plant material is placed and dissolved, Often alcohol, or petrol ether is used as the solvent, which causes some concern for Aromatherapists, as we are not sure as to how much the resins or gums may be detrimentally affected.

This method is often used to extract gums and resins. It can also be used to extract oils from flowers and buds. However, being a chemical method, it is fairly crude and as mentioned previously, a bit worrisome. Commercially, it is very inexpensive.

 

©2008 Susan Siegenthaler

 

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