Materia Aromatica

Citrus

Expressed peels, petitgrains and the citral leaves. Citrus read by source.

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Materia Aromatica · Scent

Citrus is usually taken to mean peel. The family has three sources. Expressed peel oils are mostly limonene. Leaf oils, the petitgrains, are led by esters and alcohols. A third group lies outside the genus Citrus altogether: lemongrass, lemon myrtle and lemon verbena smell of lemon because they carry citral.

01 · The Family

Terpenes, esters and aldehydes

Expressed peel oils are dominated by limonene, a monoterpene hydrocarbon with little character of its own. The differences between orange, lemon, grapefruit and yuzu sit in the minor fraction: gamma-terpinene in lemon and yuzu, octanal and decanal in grapefruit, linalyl acetate and linalool in bergamot. Cold pressing keeps this fraction intact.

Petitgrains are steam distilled from leaves and twigs. Bigarade is led by linalyl acetate and linalool. Mandarin petitgrain is led by methyl N-methylanthranilate, which gives it a dark, grape-like sweetness. The citral oils are a different case. Geranial and neral are aldehydes, sharper and more reactive than limonene, and they lead the lemon-scented grasses and leaves. Citrus oils are top notes, the most volatile materials in the library, and peel oils oxidise readily once opened.

Expressed peel

Orange, lemon, grapefruit

Limonene, with a minor fraction of aldehydes and esters that sets each fruit apart.

Distilled leaf

The petitgrains

Linalyl acetate and linalool, or methyl N-methylanthranilate in mandarin.

Citral-led

Lemongrass and lemon myrtle

Geranial and neral. Sharp and lemon-like, from plants outside Citrus.

Citronellal-led

Lemon eucalyptus

Citronellal with citronellol. A rounder, waxier lemon.

02 · The Range

Ten oils, three sources

No. 1175 · ItalyBergamot Essential Oil (Organic)Citrus bergamia · certified organicLimonene with linalyl acetate and linalool; the ester sets it apart. No. 3160 · ItalyOrganic Lemon Essential OilCitrus limon · certified organicLimonene, beta-pinene and gamma-terpinene. No. 2310 · ItalyOrange, Sweet (organic)Citrus sinensis · certified organicLimonene with myrcene and a trace of linalool. No. 2390 · IsraelGrapefruit (Organic)Citrus paradisi · certified organicLimonene and myrcene; octanal and decanal give the bitter edge. No. 3071 · JapanYuzu / Japanese MandarinCitrus junos · wildLimonene and gamma-terpinene. Tart and aromatic. No. 2450 · EgyptPetitgrain Bigarade (organic)Citrus aurantium · certified organicLinalyl acetate and linalool, with geranyl acetate. No. 2479 · EgyptPetitgrain MandarinCitrus reticulata · conventionalMethyl N-methylanthranilate over gamma-terpinene and limonene. No. 1945 · NepalLemongrass (organic)Cymbopogon flexuosus · certified organicCitral, with geraniol and geranyl acetate. No. 2182 · AustraliaMyrtle, Lemon (organic)Backhousia citriodora · certified organicGeranial and neral almost alone. A concentrated citral oil. No. 1396 · MadagascarEucalyptus Citriodora (organic)Eucalyptus citriodora · certified organicCitronellal, with citronellol and isopulegol.

03 · Side by Side

Three comparisons

One tree, three parts. Orange, Bitter (No. 2510) is pressed from the peel of Citrus aurantium and is limonene with myrcene and sabinene. Petitgrain Bigarade (No. 2450) is distilled from the leaves and twigs of the same tree and moves to linalyl acetate. Petitgrain Bigarade with Bitter Orange Flowers (No. 2451) adds the blossom to the still, and the leaf oil takes on a share of the neroli character.

Then processing. Bergamot (No. 1175) beside Bergamot Furocoumarin-Free (No. 1176) is a test of how little the removal of bergapten changes the scent. Both are led by limonene, linalyl acetate and linalool, and on a strip the two are close.

Then citral from three plant families. Lemongrass (No. 1945), a grass; Lemon Myrtle (No. 2182), a myrtle; and Balm / Melissa (No. 2060), a mint relative, all lead with citral. Lemon myrtle is the purest and sharpest. Lemongrass carries geraniol and a grassy depth. Melissa is softer and more herbaceous, with beta-caryophyllene beneath.

04 · In Practice

The opening of a formula

In natural perfumery citrus oils are the top of the composition and the first to leave it. Bergamot, lemon, neroli and petitgrain with rosemary form the classical eau de cologne. Citrus pairs with almost every family: with florals in the heart, with woods and resins beneath, with the spices in amber and gourmand accords. Because peel oils fade quickly, they are often anchored with a little vetiver, cedar or frankincense. Petitgrain lasts longer and serves as a bridge between top and heart.

For diffusion, sweet orange, grapefruit, bergamot and yuzu diffuse readily and blend with conifers and spices. In massage blends and skincare formulation, peel oils are used at low dilution. Expressed bergamot, lemon, bitter orange and grapefruit contain furocoumarins and are phototoxic on skin exposed to sunlight; the furocoumarin-free bergamots exist for leave-on use. Citral and citronellal oils are dermal sensitisers at higher concentration and are used at conservative dilution. Oxidised limonene is a sensitiser too, so peel oils are kept cool, tightly closed and used while fresh.

Essential oils are for aromatic and topical use. Dilute before applying to skin. Keep out of reach of children.