Essential Oil Extraction

It is pretty common in the bath and body products industry to go natural these days. One of the ways that companies have found successful is to eschew fragrances and perfumes, which are, by and large, synthetic and opt instead for essential oils. This results in not only a more natural end-product, but one that is often more delicately scented. However, before we can use essential oils in soaps, lotions, perfumes or other cosmetics, we have to extract them from the source plant, whether it be lavender, chamomile or vanilla. The extraction method has an effect on the essential oil - it can change it, or even contaminate it, in which case the claim of natural cannot be maintained.

There are a number of ways in which essential oils can be extracted. All, except expression are solvent based, however we will separate them out, and refer to the solvent method as using something unnatural, resulting in solvent residue.

Distillation refers to water or steam distillation. The base plant material is permeated with water and essentially boiled at 100 degrees C. Similarly in steam distillation, steam is injected, often under pressure to separate the essential oil from the plant material. This happens at temperatures above 100 degrees C. Because of this, constituents in the essential oils can often decompose into oxidative products. However, this process is considered to be natural and the yield is high, little is wasted.

Expression is often referred to as 'cold pressed'. Olive, coconut and avocado oils are often cold pressed. No heat is used, so volatile constituents remain unchanged. Yield can be low though, so this is often not a very efficient or cost effective method. There are several methods of expression that we won't go into here, but citrus oils are uniquely suited for this extraction method.

Supercritical CO2 is carbon dioxide above 31 degrees C and under extreme pressure (>72.9 atmospheres) that is used as a solvent. The supercritical CO2 bonds with the essential oil constituents in the plant material and extracts them. When the pressure is removed, the CO2 simply evaporates, leaving the pure essential oil. Since no heat is employed, the essential oil is unrefined and in its natural state. Often the scent, potency and crispness of the essential oil are enhanced as compared to steam and water distillates, scenting more closely to the original plant. While more expensive, the essential oil often goes further. The oils produced by this method are, like those extracted through expression, the purest and most natural.

Solvent extraction for our purposes here is where an organic, but not necessarily natural, solvent such as alcohol, petroleum ether or hexane (among others) is used. Often used because of cost effectiveness, it is also used for very delicate essential oils or where the essential oils are found in very minute quantities, such as rose or jasmine. This type of extraction produces a waxy substance called concrete. This concrete is then heated and dissolved into alcohol. This is then distilled in a vacuum, resulting in an absolute. Absolutes are generally very expensive. The problem for the natural community is that after extraction, quantities of the solvent may remain, often in large percentages. Hexane extraction leaves 8-10 ppm of hexane (a petrochemical) in the essential oil. This method is not viewed in the natural community as being natural and is avoided by those companies that are truly committed to natural products.

It is important to know the extraction method of an essential oil to determine not only its quality but if it can still be considered a natural product. Essential oils on an ingredient list do not guarantee natural and are often used in greenwashing exercises. The good news is that the demand for really natural products by consumers has opened up essential oils to serious scrutiny.

Avocado Oil

We hear a lot about the benefits of this oil or that oil in personal care products. One such oil that I have noticed popping up lately is avocado (Persea americana). So what's good about avocado, besides being delicious in salad or guacamole? Avocado oil is similar to olive oil in that it is not derived from the seed; rather, it is pressed from the flesh around the pit - and strictly speaking it is a fruit oil, very thin and therefore deep penetrating. It is a rich emollient with high concentrations of oleic, linoleic and alpha-linolenic fatty acids. There are many claims that it is also very rich in potassium, vitamins A, B6, C, D, E and K among others. This does not seem to be entirely truthful and much depends upon how the oil is extracted. It certainly does contain A and E as investigated by Bastista et al. Regretfully, many natural cosmetics companies have used avocado data interchangeably with that of avocado oil - there is a difference.

Extra virgin avocado oil is cold pressed (non-virgin being heat and solvent extracted) - which means that the avocado is mechanically pulverised, the resulting constituents decanted and centrifuged. This should leave you with a green coloured oil, because of the remaining chlorophyll. Unfortunately, this sometimes undergoes the refined bleached and deodorised (RBD) process which removes natural peroxides and chlorophyll, leaving a highly stable, but tasteless and pale yellow oil. This is usually done through the use of solvents and high temperatures. Do you know how that avocado oil, that you are using in your cosmetics or on your salad, is processed? Are the benefits still there?

In my opinion, besides the incredible moisturising value of avocado oil, the two most exciting properties are those of the unsaponifiable components and glutathione. Unsaponifiable constituents seem to inhibit lysyl oxidase activity and thus cross-linking in collagen - resulting in better skin tone, texture and strength. Glutathione, an amino acid with incredible anti-oxidant properties recharges spent vitamins C and E, neutralises free-radicals, is critical to the immune system and even assists in DNA repair. Unfortunately, glutathione levels decrease as we age. Thus, since your skin is a huge sponge, what better to moisturise with than avocado oil, and at the same time reap these added benefits.

References:

Batista Cedeño, A., et al (Persea americana, M). Valor nutricional y composición. Alimentaria, 1993; 63: 63-69.

AvocadoSource.com