Clusters of small round fruits the size of peppercorns, growing on a small tree in the northern mountains. Crush one and a sweet lemon scent springs out. Its Vietnamese name is màng tang, its international name may chang, and about three quarters of its oil is citral.
May chang fruit on the branch
May chang fruits are small and round, growing in clusters along the branch, and they look like peppercorns. That is why the tree carries names such as mountain pepper in English, and forest pepper in the way many Vietnamese speakers refer to it. But may chang is not a member of the pepper family. Its scent is not hot either; it is lemon.
The scientific name is Litsea cubeba. The tree belongs to the laurel family (Lauraceae), the same family as cassia and bay laurel. This detail links may chang to another aromatic tree of the northern mountains: Văn Yên cassia, told in the piece on cassia. Same family, but one tree holds cinnamaldehyde in its bark, the other holds citral in its fruit.
The may chang page in the Lê Mai library describes the fruit as small, peppercorn shaped, with a distinctive citrus scent. The oil is distilled from fresh fruit. The leaves and twigs are fragrant too, but the fruit is the part that gives commercial oil.
On the international market the oil is sold as may chang, or Litsea cubeba oil. May chang is a Vietnamese material with a familiar scent and an unfamiliar name.
A fruit the size of a peppercorn. Its scent travels much further than that size suggests.
A forest tree of the northern mountains
Litsea cubeba is a small tree of East and Southeast Asia. The library records its range as China, Vietnam, Taiwan, Indonesia and Malaysia. China is the world's largest producer of the oil.
In Vietnam, may chang grows wild and cultivated in the northern mountains: Lào Cai, Cao Bằng, Lạng Sơn, Tuyên Quang, Thái Nguyên. It is the same mountain belt that gives Lạng Sơn star anise and Văn Yên cassia. The essential oils of Vietnam page groups may chang with lemongrass and citronella: three plants that share a lemon scent but differ in their molecules.
In Vietnam's highland agriculture, the library notes that may chang has become a commercial crop supplying the citral extraction industry. That means a large share of may chang fruit does not go into a bottle to be smelled, but into a factory to separate out one molecule.
Few essential oils share that trait. The library records may chang oil as produced in very large volumes, much of it used for industrial synthesis: citral, ionone, methyl ionone, and vitamins A, E and K. Ionones are the molecules behind the scent of violet. A forest peppercorn from Lào Cai may end in a violet perfume, or in a vitamin tablet.
Picking follows the fruiting season, and the library does not yet record specific months for Vietnamese may chang. What is certain is that the fruit is picked fresh, because the oil is distilled from fresh fruit.
Distilling the fresh fruit
May chang fruit goes into the still while fresh. This differs from star anise, where the fruit is dried before distillation. Steam passes through the mass of fruit, carries the light molecules with it and condenses into a layer of oil that separates from the water.
The composition is concentrated. Geranial from 40 to 47 percent. Neral from 30 to 35 percent. Together, citral makes up about 74 percent, according to the library's safety data. The remainder includes limonene from 4.5 to 10 percent, beta myrcene from 1.5 to 4 percent, methyl heptenone from 1 to 3 percent, and linalool up to 2 percent.
With an oil that is three quarters one pair of molecules, proper storage matters. The library notes that may chang oil should be kept in a dark bottle, sealed, refrigerated, with an antioxidant where possible. Citral is an aldehyde; it reacts with air over time, and old oil changes its scent.
Fresh fruit also means the time between picking and distilling should be short. For lemongrass, the library notes that distilling right after cutting keeps a fuller scent. For may chang, the same principle applies to the fruit: the oil reflects the state of the fruit as it enters the still.
A still full of forest peppercorns, a thin layer of oil, three quarters citral.
Citral, neral and geranial
Citral is one name for two molecules with the same formula, differing only in the direction of one double bond. Citral has the formula C₁₀H₁₆O, molecular weight 152.23 g/mol. The (E) form is called geranial; the (Z) form is called neral. In nature the two always occur together.
The library describes citral in general as sharp lemon, bright and fresh. But its two halves are not identical. Neral is described as lemongrass like, softer and sweeter than geranial, with a lemony finish. Geranial carries the sharper part. The ratio between the two forms, together with whatever travels with them, decides whether a citral oil leans sharp or sweet.
The library notes that in most essential oils neral and geranial occur at roughly 2 to 3. The citral page gives a usual ratio of 40 to 60 up to 35 to 65. In may chang oil the ratio falls within that range: neral 30 to 35, geranial 40 to 47.
Citral occurs in many unrelated plants: lemongrass, lemon myrtle, melissa, lemon verbena, lemon leaf. In lemon leaf oil, geranial runs from 25 to 35 percent and neral from 18 to 26 percent, with geranyl acetate and geraniol; the library describes lemon leaf as fresh and leafy, less citrus than lemon peel oil. The same pair of molecules, set by each plant in a different frame.
Citral is easy to synthesise and also easy to isolate from may chang oil. So a lemon scented bottle on a shelf may hold citral from may chang without carrying the name may chang.
May chang beside lemongrass
The two oils carry almost the same amount of citral, but they do not smell alike. Vietnamese lemongrass oils gave 61 to 76 percent citral; may chang oil about 74 percent. Looking only at the citral figure, the two bottles are nearly the same thing.
The difference lies in what remains. West Indian lemongrass oil carries beta myrcene from 5.6 to 19.2 percent, a molecule with a green, slightly resinous edge. May chang oil carries limonene from 4.5 to 10 percent, the main molecule of citrus peel, and only 1.5 to 4 percent myrcene.
On a blotter this reads clearly. Lemongrass opens sharp, then moves to a green grassy base. May chang opens sweeter and rounder, close to lemon sweets or candied lemon peel, and holds that citrus line longer before it recedes. The library describes may chang as a fresh, sweet citrus note, close to lemongrass and melissa but more crystalline.
One green as a leaf, one sweet as a sweet. Same citral, different companions. The difference between lemongrass and citronella, told in the piece on the two grasses, is a difference in the main molecule. The difference between lemongrass and may chang is subtler: same main molecule, different minor ones.
In perfumery that difference decides placement. May chang sits easily at the top of a citrus structure without bringing grass along. Lemongrass brings the grass, and fits only when that grassy line is what is wanted.
Citral and limits on skin
The limit for may chang oil is calculated from citral. Citral is classified as a moderate sensitiser. IFRA limits citral to 0.6 percent in leave on products, rising to 1.4 percent when paired with d limonene at five to ten times the amount. Under EU rules citral must be named on the label above 10 ppm in leave on products or 100 ppm in rinse off products.
From this, the maximum dermal level for may chang oil is 0.8 percent. The figure is slightly higher than lemongrass at 0.7 percent and lemon leaf at 0.6 percent. In 10 ml of carrier oil, 0.8 percent is 0.08 ml, roughly one to two drops at 20 drops per ml.
The library adds: of 200 contact dermatitis patients, 3 reacted positively to may chang oil at 2 percent. The oil is not phototoxic. It should be avoided on the skin of children under 2 and used with care on sensitive skin. For oral use the library records a maximum daily dose in pregnancy of 56 mg, and notes interactions with some drugs through the CYP2B6 enzyme.
Storage is part of the limit too. The library notes that may chang oil should be kept in a dark bottle, tightly closed, refrigerated, with an antioxidant where possible. A bottle of citral left open to the air for long is no longer the oil that was assessed above.
One or two drops in ten millilitres. The sweet lemon of may chang needs no more than that to be present.
A fruit that looks like pepper and carries the scent of lemon.
The same citral as lemongrass, different in what travels with it.
The name is unfamiliar; the scent has long been known.