It will help to illustrate why it is important for the perfume and flavour industries to alter the original, natural composition of an essential oil if I make a comparison with wine. It is well known that there are good and bad years for wine; the same vineyard making its wine from the same vines each year will produce differences in aroma and taste from year to year. Weather and environment play their part in producing these changes, as they do with essential oil plants, altering the chemical formula of the oil produced. Furthermore, the same plant grown in another part of the world will yield a different oil again. Thus, the perfumer making up a well-known fragrance from a recipe including essential oils experiences a difficulty. For him, essential oils must be standardized, otherwise the end product would neither have the expected aroma, nor be acceptable: it is a question of adjusting (adulterating) the essential oils to achieve a legitimate aim.
Terpenes, a dominant feature in most essential oils, are sometimes removed to concentrate the remaining, more desirable constituents. The resulting compounds are known as folded or terpeneless oils, the terpenes often being used to adulterate another oil (see below).
Essential oils are also adulterated for commercial reasons – perhaps in an unethical way when operating in the field of aromatherapy. Before we bought our essential oils direct from the growers we were often asked, when ordering, ‘How much do you want to pay?’ In those days we did not realize what a complex business it was to buy essential oils, but we knew enough not to like being asked how much we wanted to pay, rather than being told the straightforward cost of the genuine oil!
What is Adulteration?
Adulteration, cutting, standardization, stretching, ennobling, sophistication – call it what you will, these terms, together with rectification (see below) mean that an essential oil has been altered in some way since leaving the still. Some of these processes are simple; some are quite complex, requiring sophisticated equipment. All these terms apply when the producer (or an intermediate further down the supply line) adds something to his essential oil to ‘stretch’ or standardize it.
Adulteration of essential oils can be carried out in a number of ways. The adulterant used may be:
1 an alcohol (to the inexperienced, the aroma is not noticeably different from the pure oil).
2 an isolate obtained from other essential oils (e.g. lemon or orange terpenes, which are available in huge quantities at extremely low cost).
3 a different, cheaper essential oil (and the claim may still be made in this (and no. 2) that the product is still a natural essential oil!)
4 a synthetic product, such as DPG (dipropylene glycol, which is colourless and odourless and is commonly added to bulk up lavender oil) or PEA (phenyl ethyl alcohol, a natural constituent of rose otto, which may be used to augment that oil).
5 an alternative, cheaper oil, somewhat similar, and substituted in toto (lavandin is often sold under the name of lavender, thus quadrupling the traders’ profit – see chapter 5).
These methods are more or less accepted in the world of perfumery; indeed, I have been told by some that an essential oil may be regarded as pure if the oil contains 51 per cent of the original material; it is a fact that an essential oil is occasionally referred to as ‘the soup’ by some perfumers. This, however, should not be tolerated in the world of therapeutics, where to have a true to its name, untampered-with essential oil is of paramount importance.
I quote from the Haarmann & Reimer Book of Perfume7
‘…bad harvests, political conflicts, exhaustion of the soil or transportation difficulties are imponderables which make it impossible for the perfumer to rely on Nature’s raw materials. Against that background, synthetic fragrance substances appear as economically indispensable substitutes for Nature’s originals.’ [my italics]
Fractionation
Here, re-distillation is carried out at low pressure in order to isolate the various chemical constituents, resulting in a terpeneless or a folded oil.
1. Terpeneless Essential Oils
These are essential oils that are concentrated by removing the comparatively inodorous and therefore (to some!) ‘valueless’ terpenes. The terpenes limonene and alpha-pinene, for example, oxidize readily and this alters their composition, resulting in changes to the aroma and to the therapeutic effects. This tendency of some constituents to oxidize makes storage of certain oils rather difficult. Also, having only slight solubility in alcohol, they give a cloudy appearance to the end product – a drawback to the perfumer and flavourist. De-terpenated essential oils are therefore ‘more soluble, more stable and much stronger in odour’.8a
Terpeneless oils are not recommended for use in aromatherapy, because not only is the wholeness (and therefore the natural synergy) of the oil destroyed, but it now contains a higher percentage of the other chemical components; some of these may be the more powerful ones with which an aromatherapist has to take care even when present in lesser quantities in a whole oil!
Terpenes are removed by distilling under reduced pressure; as these are the smallest molecules present in essential oils they are the first to evaporate, eventually leaving the terpene-free oil in the distilling flask.
2. Folded Essential Oils
These are concentrated oils, differing from terpeneless oils in that they still contain varying amounts of terpenes. The process is halted wherever the perfumer wishes, with varying, known, percentages of terpenes being removed. The oils are referred to as singlefold, twofold – up to fivefold (where the greatest percentage of terpenes have been removed).8b
Essential oils are fractionated to remove other constituents too, e.g. bergapten (or bergaptene) which is a furocoumarin, not a terpene (see chapter 3). Fractionated oils are of use only in perfumery and the food industry, although some aromatherapists use bergapten-free bergamot oil because bergapten is the chemical responsible for photo-sensitization (yet use in sunlight is its only contra-indication! – see chapter 6). In my opinion this goes against the basic belief in aromatherapy that the whole, natural, synergistic mix of components, as extracted from the plant, should be used for maximum therapeutic benefit.
Rectification
Rectification (‘putting right’, or ‘cleaning up’) is carried out by redistilling an essential oil which either has been contaminated with undesirable plant products (such as plant dust) through careless distillation procedure, or contains colour or aroma molecules undesirable for the perfumer. The end product is not necessarily an improvement in quality8c but is what the perfumer wants.
Synthetic Oils
Apart from adding synthetic components to an essential oil, a chemist can put together only synthetic molecules, to simulate the aroma of an essential oil, and, whatever plant name may be bestowed upon them, many cheap perfumes (and ‘aromatherapy’ toiletries) are totally synthetic (as indeed are many flavourings). It would be wrong of me to say that these have no effect whatsoever, as any smell, from whatever source, has an effect on the mind – even a bad smell – and can make one feel