How To Store Perfume, According to Science

In this edition, we asked Olivier R.P. David, an associate professor of organic chemistry at the University of Versailles - Paris-Saclay and a member of the scientific committee at the Osmothèque, about the best way to increase the shelf-life of fragrances.

David teaches aspiring perfumers, cosmetic scientists, and flavorists in the FESAPCA Master's program at the École supérieure du parfum.

As a member of the scientific committee at the Osmothèque, the international perfume conservatory in Versailles with 4,000 perfumes, including 800 that are no longer found, he is also an "osmothécaire" who helps preserve and share the history and science of perfumery.

David is also part of the NEZ collective and co-authored "Le Grand Livre du parfum". His research at the Institut Lavoisier de Versailles focuses on the eco-responsible synthesis of odorant compounds and extraction of rare raw materials using green solvents.

Here's our short interview:

How does the Osmothèque store its valuable vintage perfumes to protect them from deterioration?

Before answering the question, one point to be corrected, Osmothèque doesn't store any 'vintage' perfume, we only have freshly re-weighted perfumes according to the original formulas. Although when we say 'freshly re-weighted' it could be several years old since not all perfumes are reconstituted every year!
In any case, the storage is at 12°C in artificial wine cellars with brown glass to prevent exposure to the light. Additionally, each brown bottle is flushed with argon to exclude as much air as possible to avoid contact of the perfume with oxygen.

What chemical processes occur inside a perfume bottle as the fragrance ages?

Several reactions are occurring, some are inevitable with the interactions between the fragrant molecules:
- formation of Schiff-bases (that we call imines in chemistry) between any aldehydes and methyl anthranilate (the color will turn orange)
- formation of hemiacetals and acetals between aliphatic aldehydes and ethanol (important already during the maturation/maceration processes so the aldehydic note becomes rounder, smoother)
- reaction of esters with the solvent, ethanol, what we call 'transesterifications' esters of methyl, propyl, etc will be exchanged by an ethyl after a very slow 'switching' with ethanol.

Some have to be slowed down as much as possible, as we cannot prevent them, like all types of oxidations, which obviously need some oxygen, and are triggered by heat and light.
Oxidation of ethanol itself gives the typical 'aged perfume' off-note, recalling fresh walnuts, with the formation of ethanal or acetaldehyde and the corresponding diethyl acetal.

Which types of perfumes age well, and which ones deteriorate quickly?

Citrus with high contents in terpenes (limonene, pinene, etc.) are prone to oxidations, so fresh colognes are very sensitive. By a mechanism that is not elucidated, oakmoss and other moss-type ingredients tend to accelerate the oxidation of other molecules without being affected themselves! So chypre and fougère tend to become mossier and 'stiffer'.
On the contrary, vanillin and eugenol are natural anti-oxidants, so ambery and spicy perfumes are usually less affected by degradation. So are the leather perfumes (birch tar, and other smoked notes) since the phenolic molecules at the origin of the smoky facets are also good anti-oxidants!

Have antioxidants like BHT and UV filters like PARSOL® MCX significantly increased the shelf life of modern perfumes?

Yes, they have! Actually, the synergistic effect of using an anti-oxidant in conjunction with a UV filter was proven. The best approach is to prevent contact with oxygen, which explains why the old 'atomizers' that used pressurized butane to exclude any oxygen from entering are usually the best-preserved vintages.

How can the average consumer increase the shelf life of their beloved perfumes?

My simplest advice would be: "Keep the packaging." Having the bottle protected from light when storing it in its packaging is already very efficient! The bottle may be very elegant, but it is not a deco item, and the bathroom spotlights are very bad for it!