Tonka Bean

The tonka tree is a large rainforest tree that can reach 25 to 30 metres, bearing small pink to purple flowers and, later, a single-seeded, almond-shaped pod. When the pod is opened it releases a black, wrinkled seed about 3 to 4 centimetres long, which smells strongly of vanilla, freshly cut hay, almond and sweet spices. Traditionally the seeds are soaked in alcohol such as rum and dried, which brings a white crystalline coating of coumarin to the surface. They are normally grated in tiny amounts with a microplane, the way nutmeg is used.

Dipteryx odorata is native to northern South America, in the Amazon basin and neighbouring Guiana region, and is found in Venezuela, Colombia, Brazil, Guyana and Peru. It grows in tropical rainforest and is also cultivated, mainly in Venezuela and Brazil, with some plantings in Nigeria and other tropical countries. Local names include cumaru in Brazil. The seeds are collected from the forest floor after the pods fall, and the tree's timber, which is very hard and durable, is also used.

Indigenous peoples of the Amazon region used the tree and seeds for flavour, perfume and traditional remedies long before Europeans arrived. After contact, the seeds were exported to Europe, where in the eighteenth and nineteenth centuries they were used to scent tobacco and snuff and as a cheaper substitute for vanilla in cooking and perfume. The name tonka is thought to derive from a word in a Guianese Indigenous language.

In 1954 the United States Food and Drug Administration banned the use of tonka bean as a food additive because it contains coumarin, and the European Union and other jurisdictions limit coumarin in foods and drinks. Even so, the bean has remained a favourite with chefs, perfumers and tobacco makers, and it appears in fine-dining desserts, often in very small grated quantities, and in perfumery. Regulations vary by country and are still debated, and cooks should check local rules.

Tonka bean is grated in tiny amounts into custards, panna cotta, ice cream, chocolate, shortbread, sauces and syrups, where it adds a warm vanilla-almond-cinnamon-like note. It pairs well with chocolate, cherry, coffee, pear, caramel and cream. It is also used to infuse spirits and in perfumery, soap, and the scenting of tobacco. A single bean is potent and is generally used in fractions, spread across many servings.

Tonka bean is used as a flavouring in tiny amounts, so it contributes almost nothing nutritionally. Its fragrance comes mainly from coumarin, a compound also found in cinnamon, cassia and sweet clover. Coumarin has been studied for its effects on the liver and blood, and in some people and in animal studies, high intakes can cause liver damage. For that reason the amount in food is restricted by regulation in many countries. It is best viewed as a rare aromatic, not a food source.