Tonka

The tree, Dipteryx odorata, is semi-deciduous and is pollinated by insects. The tree belongs to the pea family, Fabaceae, and is also called cumaru. The seeds are black and wrinkled and have a smooth, brown interior. Each developed fruit contains one seed.

Tonka bean in PREMIEREPEAU

Tonka and coumarin are among the materials listed for Albâtre Sépia, composed by Florian Gallo. Albâtre Sépia is also part of the Discovery Set.

The tree and its fruit

Dipteryx odorata is found in present-day Venezuela, northern Brazil, Colombia, Suriname and the Guianas, as well as the nearby islands of Trinidad and Tobago. The tree grows to a height of up to 25-30 m (82-98 ft), with a trunk of up to 1 m (3 ft 3 in) in diameter. The bark is smooth and gray, whereas the wood is red. The leaves are alternate and pinnate, with three to six leathery, glossy, dark green leaflets, and the flowers are pink.

The fruit resembles a small mango, ripening from dark green into yellow and mahogany. Its fibrous yellow pulp encases a fuzzy, peach-like pit that holds a smooth, black seed. The name tonka bean is derived from the Tupi and Galibi languages of Indigenous South America. The tree also yields a durable hardwood known as cumaru, which is exported for flooring and furniture.

Where the smell comes from: coumarin

The scent of tonka comes from coumarin (C₉H₆O₂, molecular weight 146.14, CAS 91-64-5). The seeds normally contain about 1-3% of coumarin, but can rarely reach levels of up to 10%. Coumarin is also present in lavender, cinnamon, licorice, strawberries and cherries.

Coumarin belongs to the benzopyrone chemical class and is considered a lactone. Coumarin is a colorless crystalline solid with a bitter taste. Coumarin can be prepared by several name reactions; the Perkin reaction between salicylaldehyde and acetic anhydride is a popular example.

Many anticoagulant prescription drugs, such as warfarin, are based on 4-hydroxycoumarin, a chemical derivative of coumarin; coumarin itself has no anticoagulant properties.

Use in food and tobacco

In France, tonka beans are used in cuisine, particularly in desserts and stews. The flavour has been described as a complex mix of vanilla, almond, clove, cinnamon and amaretto. The beans are still used to flavor some pipe tobaccos.

Food rules and safety

In large infused doses, coumarin may cause hemorrhages, liver damage, or paralysis of the heart. It is therefore controlled as a food additive by many governments.

In the United States, 21 CFR 189.130 deems food containing any added coumarin, as such or as a constituent of tonka beans or tonka extract, to be adulterated, based on a Federal Register order of 5 March 1954 (19 FR 1239). European Regulation (EC) No 1334/2008 sets maximum limits for coumarin in food, among them 15 mg/kg in fine bakery ware (traditional and seasonal bakery ware citing cinnamon excepted) and 5 mg/kg in desserts.

Cultivation

The cumaru tree is a light-demanding calcifuge tree which grows on poor, well-drained soils. The best growth is reached on fertile soils rich in humus. A tree yields about 1.0-3.5 kg (2.2-7.7 lb) of beans per year, but produces a large volume of seeds every four years.