Monday, August 12, 2013

Essential Oils vs. Extracts

Here's a question that I'm frequently asked: "What's the difference between an essential oil and an extract?"  "If I should avoid grapefruit seed extract, should I also avoid grapefruit essential oil?"

What are Essential Oils?
The term "essential oil" has a very specific meaning. Essential oils are the concentrated volatile aromatic compounds of a plant, typically consisting of terpenes, esters, aldehydes, ketones, alcohols, phenols, and oxides. In other words, the aromatic compounds of the plant are removed and separated to create an oil-like substance.  (Although essential oils are not technically oils, as true oils are made up of lipids.) Essential oils are typically extracted through the process of steam distillation.  Plant matter is placed in a big vat with water and boiled...the steam arises and through a system of tubes. As the steam cools, the water collects to the bottom of the tank and the essential oils arise and collect in a separate tank.  (The water that's collected is known as a hydrosol and contains trace amounts of the essential oil and other components from the plant.) The only exception to steam distillation is with citrus fruits, where the essential oil is sometimes pressed from the rind of the fruit.  (Called cold-pressing.)

What are Extracts?
There are several types of extracts.
  • Infusions
    • An infusion is made when the plant material is let to steep in water or oil for a period of time.  A water-based infusion is made just like you'd make a cup of tea--boil the water and add the herbs to steep for anywhere from 5 to 30 minutes.  With an oil infusion, the steeping time is much longer, from days to weeks.  
  • Tinctures
    • A tincture is an alcohol-based extract. The plant material is steeped in a solution of (usually) 50% alcohol. The plant material steeps for days to weeks to extract compounds from the plant.  
  • Glycerites
    • These are liquid extracts in glycerin.
Essential Oils that Aren't Really Essential Oils

You may see a few ingredients listed as essential oils, when in fact, they aren't truly essential oils. Take for instance vanilla.  The "essence" of vanilla is difficult to extract via steam distillation, so it's typically extracted through steeping in alcohol (most commonly) or in oil.  This is the traditional vanilla extract that you'd use in cooking.  This is the least concentrated form of vanilla extract.  But, for a more concentrated form of vanilla, there's vanilla oleoresin. (Sometimes you'll see it listed as essential oil.)
  • Oleoresin
    An oleoresin is created by taking an alcohol-based extract and evaporating out the alcohol.  You're then left with a thick resinous material that's a more concentrated form of the aromatics that the plant provides.  Two common oleoresins are vanilla and rosemary.  Vanilla oleoresin is commonly used in personal care products as a scent.  Rosemary oleoresin (also listed as rosemary extract) is used as an anti-oxidant in foods and personal care products, helping give oils a longer shelf life. (Do note that it is an anti-oxidant, not a preservative.  It will help keep oils fresh but it does not stop bacterial growth.)
  • Absolutes  
    Finally, there are absolutes. This is the most potent and concentrated form of extracts.  Absolutes are typically extracted with a solvent like hexane to create a waxy material called a concrete.  The concrete is mixed with alcohol to further extract the aromatic compounds.  Then, the alcohol is evaporated out and a highly concentrated oil known as an absolute is left behind.  Sometimes people will mistakenly list an absolute or oleoresin as an essential oil, whereas they are technically not an essential oil.  Plants that are typically extracted as absolutes instead of essential oils include vanilla, jasmine, tuberose, oak moss and mimosa.  When it comes to roses, both steam-distilled essential oil and absolutes are made.  There are actually absolutes of honey as well, that will extract the delicate fragrance notes from different types of honey.  
Fake Extracts

There are some ingredients that you'll see listed as "extracts" on a product, when they're not really an extract.
  • Japanese Honeysuckle Extract is not a true extract but a highly synthesized preservative.  You can read more about it here.
  • Grapefruit Seed Extract is not a true extract, but a quaternary ammonium compound that's also used as a preservative.  You can read more about it here. (Not to be confused with grape seed extract, which is a totally different thing, extracted from grapes, not grapefruits. Grape seed extract is a true extract.)
Vegetable/Carrier Oils

Vegetable or Carrier oils are true oils, composed of lipids (fats). These include sunflower, jojoba, safflower, almond, olive, coconut. They are either solvent, or, preferrably, cold-pressed from the seeds, nuts, or fruit of certain plants.  Some carrier oils sound like essential oils, when they are not.  For instance rosehip seed oil is not an essential oil but a vegetable carrier oil.  After the rose has blossomed and created a rose "hip", inside this hip are hundreds of tiny little seeds.  These seeds are taken and pressed to create rosehip seed oil.  It doesn't smell like roses, but has a nutty, seed-like aroma.  Red raspberry seed oil is also commonly confused. It is pressed from the raspberry seeds and while it does have a mild raspberry aroma (somewhat like raspberry leaf tea) it is not an essential oil and is used for moisturizing properties, not for scent or aromatherapy.