Bourbon essential oils

Bourbon – essential oils not kings or biscuits!

‘Bourbon’ was the name of the royal family in France (until the French revolution!) and also, for a time, the monarchies in Spain and Italy. On the other hand, bourbon biscuits were developed in 1910 by a British company called Peak Freans. The company deliberately chose to name their new biscuit after the royal house of Bourbon but that ls where all similarity ends.

So, what’s the link to essential oils? In 1649 an island in the Indian Ocean, east of Madagascar and 175 km (109 miles) southwest of Mauritius was named Île Bourbon (after the French royal house). In 1848 the island became Île de la Réunion and, as an overseas department of France, the name has remained unchanged.

What about essential oils you ask? In the mid-19th century, when the Damask rose became rare and its essential oil costly, perfumers set off in search of new plants with rose-like odours. Soon, geranium, palmarosa and lemongrass were being imported from the East Indies. In 1819, the rose geranium, having become a sought-after raw material in perfumery, officially found its place on the perfumer’s organ*. In 1880, it was introduced to Réunion Island, at altitudes between 400 and 1200 metres, where sugar cane and vanilla could not be grown, where it was christened Bourbon geranium, a nod to the island’s former name.

Bourbon geraniums are grown as perennial crops spread over more than three years. The plant is harvested several times a year between October and April. The traditional hydrodistillation of the leaves and stalks produces Bourbon geranium essential oil, which has a full, green, floral, rose odour with minty-fruity undertones. It is less powdery and more lemony than rose. This refined fragrance means that Bourbon geranium is still the form preferred by perfumers.

Egypt and China have become major producers of geranium essential oil but, arguably, these essential oils lack the refinement of geranium Bourbon. Geranium essential oil from Egypt is sweeter, more floral and not as minty but displays a stronger rose note. Whereas the essential oil from China possesses an instant hit of fresh geranium and rose, followed by a rich, slightly fruity character, with a distinct metallic, dewy, rosy floral note. However, some consider the heart and base notes to be weak and lacking in comparison to the Bourbon or the Egyptian offering.

In terms of chemistry, geranium essential oils are alcohol rich, with citronellol the major component. Geranium essential oil from China typically contains around 40% citronellol, that can be up to 50% more than commonly found within the Bourbon essential oil and about 25% more than Egyptian material. 

Citronellol is a key natural constituent of rose, the amount present can vary greatly but it has been found at up to 40% in rose essential oils. It has a fresh, floral, clean, rose fragrance and is one of the so-called ‘rose alcohols’, used by perfumers to create floral scents such as rose and lily of the valley.

The ester, citronellyl formate is found in all three geranium essential oils but at higher levels in the oil from China (10–15%). It has a very clean fresh smell with a hint of rosiness and fruitiness about it.

Geraniol is another alcohol found in all three geranium essential oils, but this time at higher levels in geranium Bourbon (up to 30%). The scent is plummy, berry-fruit, rose petal, sweetly fresh and a little waxy. Perfect for the job of providing the sweet, rosy, floral complement to citronellol’s green, petal freshness.

A third significant alcohol found in all three geranium essential oils is linalol (or linalool as the perfumers call it). This has a fresh, floral-woody, sweet, citrus aroma and is the component that gives the ‘lift’ in an overall heavier composition.

It would be wrong to think that the smell of an essential oil is always due to the major components. Found in rose essential oil at levels below 0.15%, the ketones beta-ionone, beta-damascenone and beta-damascone make a significant contribution (>90%) to the scent of the essential oil. The smell of grapefruit essential oil is primarily due to the presence of a thioterpineol (a type of mercaptan) at a level of <1part per billion.

And while talking about roses, the first members of the “Bourbon” group of garden roses originated on Réunion (then still Île Bourbon, hence the name) from a spontaneous hybridisation between Damask roses and Rosa chinensis which had been brought there by the colonists. The first Bourbon roses were discovered on the island in 1817.

Another essential oil produced in Réunion is vetiver, indeed at one time Réunion was the world’s second largest exporter of vetiver essential oil. Many regard vetiver Bourbon with the same high regard as geranium Bourbon, due to its particular heavy, woody, earthy odour with sweet-sour accents and woody-balsamic undertones. The chemical composition is complex, with the major components having quite different names to those with which we may be more familiar eg

Zizanol

Vetiselinenol

Alpha-cadinol

Alpha-vetivone

Beta-eudesmol

Khusenic acid

Enjoy a bourbon biscuit as you enjoy your bourbon essential oils – you may find they go well together!

* Perfumer’s organ: was an instrument invented by the French chemist Septimus Piesse, in which the keys of a piano activated one of 46 different odours. In 1857, in his book The Art of Perfumery, Piesse used music to describe how notes and smells can work together: “There is, as it were, an octave of odours like an octave in music; certain odours coincide, like the keys of an instrument.”

Ian Cambray-Smith FIFPA, MSCS, BSc, MSc, PGCE