Tonka beans are the seeds of a South American tree, rich in coumarin, with an aroma of vanilla, almond, cherry and hay. Pastry chefs grate them into cream and chocolate; the US bans them in food.
What it is¶
The tonka bean is the single seed inside the fruit of the cumaru tree, Dipteryx odorata, a tall rainforest tree of northern South America. The fruits are gathered after they fall, the hard shells are cracked, and the almond-shaped seeds are dried. Traditionally they are then soaked in rum or another spirit and dried again, which brings coumarin to the surface as a fine white frosting.
Finished beans are 3–4 cm long, black, deeply wrinkled and slightly glossy. Their intense smell comes from coumarin, a compound first isolated from tonka beans in 1820; its name comes from coumarou, a French Guianese name for the tree.
Origins and history¶
Tonka beans were used by Indigenous peoples of the Amazon and the Guianas, and became a commercial product in the 19th century, when they were exported to Europe and North America for flavouring snuff and pipe tobacco, and as a cheap substitute for vanilla in foods and imitation vanilla extracts.
Coumarin itself was synthesised in 1868 by the English chemist William Henry Perkin, and it transformed perfumery: Houbigant's Fougère Royale (1882) was built around it and gave its name to the fougère family of fragrances. Tonka beans are still used in perfume and tobacco.
In food, tonka's reputation changed after research in the mid-20th century showed that large doses of coumarin damaged the livers of laboratory animals. The US banned coumarin as a food additive in 1954. In Europe tonka remained legal, and French pastry chefs in particular revived it from the 1990s onwards as a fashionable dessert flavouring.
Flavour and aroma¶
Tonka smells like a cross between vanilla, marzipan, sour cherry and freshly cut hay, with notes of cinnamon, cloves, caramel and tobacco. The fresh-hay note is coumarin itself — it is the same smell as drying sweet grass or woodruff. It is extraordinarily powerful: a single bean can perfume several batches of custard.
In the kitchen¶
Tonka is used in minute quantities, almost always in sweet dishes with fat.
- Grate it like nutmeg on a fine rasp: a few passes, perhaps 1/8–1/4 of a bean, is enough for 500 ml cream or milk.
- Infuse it: warm a whole bean in 500 ml cream or milk for 15–20 minutes, then remove it, rinse, dry and reuse; one bean can be infused several times.
- Custards and creams: crème brûlée, panna cotta, crème anglaise, ice cream.
- Chocolate: ganache, chocolate mousse and brownies; tonka flatters dark chocolate and coffee.
- Fruit: poached pears, roast plums, cherries and apricots.
- Baking: shortbread, madeleines and financiers, grated into the butter or sugar.
- Savoury: some chefs grate a little over scallops, duck or root-vegetable purées; use with great care.
💡 Grate cold
Beans grate more cleanly when dry and cold. Store your grater with the bean in a small jar so you never need to wash off the dust — and grate over the pan, not the worktop, to keep the quantity under control.
Buying and storing¶
Whole tonka beans keep for years in an airtight jar in a cool, dark place, gradually becoming harder. A whitish crystalline bloom is coumarin, not mould. Never buy tonka ready-ground.
Substitutes¶
Good vanilla with a drop of bitter-almond extract gets close. A little ground mahleb shares the cherry–almond and coumarin notes. For the hay character, a few dried leaves of sweet woodruff are traditional in German cooking, though they also contain coumarin.
Pairs well with¶
Chocolate, coffee, cream, milk, butter, caramel, honey, rum, cherries, pears, plums, apricots, rhubarb, almonds, vanilla, cinnamon, cardamom, nutmeg and orange peel.
Health and safety¶
⚠️ Legal status and coumarin
Tonka beans are rich in coumarin, which in large doses can cause liver damage in sensitive people. In the United States, coumarin has been prohibited as a food additive since 1954, and the FDA treats food containing tonka beans as adulterated; tonka is therefore not legally sold as a food ingredient there. In the UK and EU, tonka beans are legal, but adding pure coumarin to food is prohibited and maximum coumarin levels apply to certain foods containing coumarin-rich ingredients.
The European Food Safety Authority set a tolerable daily intake for coumarin of 0.1 mg per kilogram of body weight. Coumarin content in tonka varies, but the tiny amounts used to flavour a dessert — a few gratings shared between several people — are small. The risk comes from treating it like vanilla and using it generously or daily. It is sensible to avoid it in pregnancy and for anyone with liver disease. Children, with their lower body weight, reach the limit faster. See coumarin-in-cinnamon, which covers the same compound in cassia.