Beward of 'old oils' and store oils properly -- from another group

[Guest guest]

Anya here: I have permission from the original author/listowner (from

another ) to repost these here. Hope it starts a lively

discourse on how to store oils, and why we should avoid buying 'old' oils.

 

Original Message:

I want to discuss " Best before date / expiry date of essential oils. "

I was in my local chemist the other day and a brand of

oils that I had not seen for a few years was being

displayed on the front counter, these oils are TGA

(therapeutic goods administration) licensed oils, the

Bergamot and Sweet orange oils both had best before

dates of late 2007, The peppermint had a best before

date in late 2009. The oils which were for sale were

in cardboard boxes on top of the counter under lights.

I live in Perth W.Australia, for the last week we

have been experiencing 38 -41 degrees C.

 

I am going to contact the TGA but would really

appreciate comments from those of you involved in e.o

sales / production. { } recommends in new book

refrigerating citrus oils and using within

1 year and only keeping other oils for 3 years.

 

Look forward to your responses.

--

Listowner/Chemist responds to the above post:

Thanks for bringing up this topic. I have been scandalised in the past when

visiting practising AT's, about the state of their oils, and the condition

in which some oils are in when they are purchased. Let me explain further -

sorry if this is long and involved but I want you to get the full picture,

not just some unqualified guideline from a book.

 

If you have been following the EU legislation (EU legislation is generally

mirrored by equivalent laws in Australia after a period) you will know that

sixteen sensitisers (citronellol, geraniol, limonene etc) have been

identified in essential oils, which has resulted in a requirement for

labelling in retailed products under the EU Cosmetics Act, if they are

present in product at a value over an extremely low concentration. Many of

us essential oil chemists think that these sensitisers are not the actual

materials themselves, but oxidation products arising from the identified

materials.

 

Again, many of us have also said that if anti-oxidants were added to

essential oils containing certain of these sensitisers as a requirement of

good manufacturing practice - as is carried out in the flavour industry -

then the perfume and aromatherapy industries wouldn't be in such trouble

with these problems. We wonder why RIFM did not recommend this 20 years ago.

 

Basically the formation of hydro-peroxides by oxidation has been identified

as causing the problem with linalol (and by inference, linalol containing

essential oils such as lavender, bergamot, rosewood, ho etc. although this

is not completely certain since evidence to the contrary also exists).

 

But much more certainly, with Citrus oils, the oxidation of dextro-limonene

to produce hydroperoxides which cause skin sensitisation (and degradation

of the odour characteristics, hence the quality of the oil) has been

highlighted by Danish dermatologists in published papers. Good

manufacturing practice therefore to restrict peroxide values in citrus oils

by adding anti-oxidants, can be followed on the IFRA website. Normally in

industry we store citrus oils in the dark in topped up tightly sealed

containers in cool conditions at 5-15 C under nitrogen to prevent

oxidation. We recommend consumption within 6 months, or at least

re-assessment after that period.

 

Again with absolute certainty, Pinaceae oils suffer the same problem with

the oxidation of their laevo-limonene and delta-3-carene contents, to

produce hydro-peroxides again responcible for skin sensitisation and

artefact formation in the oils. Again the IFRA website gives standards for

peroxide limits that the perfume industry should work to when using Pine

oils. In a perfect world, the many Professional Aromatherapy Organisations

that there are, or the few Essential Oil Trade Councils, should recommend

that aromatherapists do not use citrus and pine oils with peroxide values

over a certain defined limit - but few organisations have the technical

expertise to recommend this, and policing the policy would be difficult, if

not impossible to carry out. Self-policing is our only chance here....

 

Peppermint oils seem to suffer this also, from oxidation of the limonene

content as above, but also in my experience, from resinification.

Resinification is the other phenomena that occurs when essential oils

oxidise, where dimers, trimers and longer polymers of the terpenes are

formed. These materials are examples of further compounds generally not

detected by GC-MS (just in case you have been brainwashed by suppliers into

thinking that a GC trace will tell you everything about an oil). Perhaps

because they are not easily measurable, the formation of polymers seems to

be rarely mentioned in essential oil literature, and yet it is a universal

problem.

 

Storage in a 'fridge at 1-2 C is pretty well essential for all absolutes,

citrus oils, peppermint oils and pine & fir oils, and this happens in all

the labs that I currently work in. Other oils should be stored at 15C max

in the dark in full tightly stoppered bottles and checked after a few

months if they cant be stored in a 'fridge. Storage under the hot

conditions you describe in your mail means that after a while the bottles

will be full of oxidised & resinifed terpenes and aromatics, and the

contents have little resemblance to the description on the label, and

little therapeutic value. There is an interesting paper on oxidation of

lemon oil coming out shortly in the IJA I believe, which adds weight to

this argument.

 

In my opinion, keeping oils for as long as 3 years, even in cool

conditions, is very poor advice - it is far too long. You can confirm this

yourself, since, I believe, dip-strips for essential oils which indicate

peroxide values which are above recommended limits, are now commercially

available - they will allow you to monitor your oils for degradation.

 

Anyway, you are onto something here - go for it and make a big fuss! We

can all benefit from better guidelines on this topic.... any help you need

please contact me further.

--------------------------------

Anya here again -- Chris, I think this information is important enough to

be in the files section -- what do you think?

 

Plus, I have to review another post on the subject, and if it is a

followup, I'll post that also, as Part 2.

 

 

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