This is the third and final part of the series ‘The bitter orange tree: bigarade, petitgrain, orange leaf, neroli, and orange blossom’.
If rose is the queen and jasmine the king, then bitter orange flower is the princess of all flowers. The youthful, radiant, and romantic scent of these vernal blossoms captures the spring time. The main extracts of bitter orange (Citrus aurantium subspecies amara) flower are neroli oil and orange blossom absolute.
Legend has it that neroli oil is named after the princess of Nerola, Marie-Anne de la Trémoille, who was known to have perfumed her gloves and bath with the essential oil of bitter orange flowers. Neroli oil has a fresh floral profile with green and spicy tone that recalls petitgrain oil. But despite their olfactory resemblance, the contents of ocimenes, β-pinene, limonene, linalool, and linalyl acetate of neroli oil are higher than those of petitgrain oil. Moreover, neroli oil also possesses the jasmine odorant cis-jasmone as well as the exotic jasmine note of 1H-indole and the Concord grape of methyl N-methylanthranilate that differentiate it from petitgrain oil. And interestingly, despite coming from a citrus plant, nootkatone and other typical components of citrus oils are not found in neroli oil.
Production of neroli oil and orange blossom absolute concentrates in Tunisia, Morocco, and Egypt in April. It starts from manual picking. The flowers are picked by hand to avoid damaging the immature flower buds, which will be collected in subsequent harvests. After distillation, around 850 kg to 1000 kg of flowers yields 1 kg of neroli oil. The Tunisian oil has the fresh floral note of orange flower and is reminiscent of freshly ironed linen. The Moroccan variety possesses the fresh floral sweetness of orange flower, but also harbours green and animalic aspects.
To obtain orange blossom absolute, around 1000 kg of flowers are loaded into an extractor with a solvent for heating. The solvent is later removed by evaporation, leaving the liquid ‘concrete’ of orange blossom, which solidifies at room temperature due to the presence of wax in the flowers. The collected concrete is melted down and mixed with alcohol at 60°C. After an hour of mixing, it is cooled down to 0°C to remove the solidified wax from the mixture. Finally, the alcohol is removed by evaporation to yield roughly 1 kg of orange blossom absolute. Tunisian orange blossom absolute is floral, warm, sensual, and heady — typical of orange flower. The Moroccan origin is also warm, but more animalic and indolic. Moreover, the by-product of steam-distilled flowers can be solvent-extracted to produce orange blossom water absolute, which has a harsher orange blossom character, is less indolic, and not as heady when compared to the absolute.
There are several aspects that impart distinguishing features to neroli oil and orange blossom absolute. The hydrocarbons such as α-pinene, β-pinene, myrcene, limonene, and ocimene confer the bright citrus note. Particularly important are the ocimenes, which provide a very fresh citrus note with a subtle green accent. These compounds make up about 40% of neroli oil whose sparkling and diffusive character is used to add freshness to a composition. In contrast, the hydrocarbons constitute only around 6% in the absolute that is, nonetheless, employed to boost the floralcy of other components.
Meanwhile, the alcohols are a class that contributes to the floral notes. These include linalool, phenyl ethyl alcohol, α-terpineol, citronellol, nerol, geraniol, nerolidol, and farnesol. Amongst these, linalool provides much of the character impact.
As for the esters found in extracts of bitter orange flower, they serve as accents to modify the citrus notes. Such esters are linalyl acetate, methyl anthranilate, neryl acetate, citronellyl acetate, and geranyl acetate. Methyl anthranilate, also a nitrogenous compound, is the most important of its kind and can be found up to 10% in the absolute; its fruity and floral character is essential to both neroli oil and orange blossom absolute.
Yet, another minor but important class of compounds is phenol. Eugenol is an important phenol in extracts of bitter orange flower. Despite being a minor constituent, its spicy clove note imparts a kind of brightness and natural character to the flower.
Interestingly, important nitrogenous compounds found in extracts of bitter orange flower are the aforementioned methyl anthranilate, indole which is a potent floral chemical with animalic character, and pyrazines that impart green, dry, and earthy character. The high-impact 2-isobutyl-3-methoxypyrazine, for example, confers a green facet that recalls galbanum oil and green peppers to neroli oil. The pyrazines are, perhaps, what give orange blossom extracts their peculiarity that can add a long-lasting, signature freshness to the top note.
Neroli and Orange Blossom in Perfumery
Such insights into the chemical compositions of bitter orange flower are also essential to the reconstitution of an orange blossom or neroli note. This is because extracts from bitter orange flower are very expensive and, in most cases, can only be afforded in small amounts.
A classic reconstitution of the orange blossom note, for instance, is through a Schiff base formed by a reaction between an aldehyde (–CHO) and an amine (–NH2) such as methyl anthranilate. One of the most widely used Schiff bases in the reproduction of orange blossom and neroli notes is Aurantiol, which is produced by the reaction between hydroxycitronellal and methyl anthranilate. The only problem with Schiff bases is that they are strongly yellow and would pose a problem, should discolouration be a concern. In any case, they can be further used in compounding orange blossom or neroli notes in bases or fragrance composition itself.
New odorants for orange blossom or neroli notes have also been developed and could lend special signature to such fragrance bases, and hence fragrance compositions. Nerolione® is an example of a high-impact, very stable, non-discolouring orange blossom material. Even in small amounts, it performs excellently in challenging bases of household and personal care products. But it can also be used in fine fragrances to brilliant effects. Perfumer Maurice Roucel dosed a few parts of Nerolione in Insolence (Guerlain, 2006) and brought out the floral radiance of violet. It may not provide a scent of its own in a formula, but it creates a synergy with floral and fruity notes, giving a blooming effect.
Neroli and Orange Blossom in Perfumes
Moreover, we also find orange flowers in compositions of other styles such as lavender water, aldehydic, chypre, and amber types. These include Chanel N°5 (1921), Arpège (Lanvin, 1927), Fleurs de Tabac (Cherigan, 1929), Vol de Nuit (Guerlain, 1933), Fleurs de Rocaille (Caron, 1934), Miss Dior (1947), English Leather (1949), and Fidji (Guy Laroche, 1966). Another interesting example is the development of a jasminic facet of neroli oil in 24 Faubourg (Hermès, 1995). The sensual floral character of orange blossom is key to masterpieces such as Après L’Ondée (Guerlain, 1906) and L’Heure Bleue (Guerlain, 1912).
Sources: P&F Vol.6 June/July 1981 by Felix Buccellato, P&F Vol.16 November/December 1991 by Mans H Boelens and Antonio Oporto, P&F Vol.9 February/March 1995 by Danute Pajaujis Anonis, P&F Vol.34 March 2009 by Jeb Gleason-Allured, Scent and Chemistry The Molecular World of Odors, west-crete.com