African locust bean

Parkia biglobosa is a spreading, deciduous savanna tree that can grow 10 to 20 metres tall, with feathery leaves and distinctive, ball-shaped red flower heads hanging on long stalks. The long, brown, flattened pods are packed with about a dozen shiny black or dark brown seeds embedded in a sweet, powdery yellow pulp.

The raw seeds are hard and astringent. Traditionally they are boiled, dehulled and fermented for a few days, then pressed into balls or cakes. The result is a dark, sticky, strongly aromatic paste or dried cake with a savoury, umami-rich flavour often compared with cheese or aged soy, and it is sold in markets as daddawa, iru or soumbala, in whole or ground forms.

Parkia biglobosa is native to the savanna belt of West and Central Africa, from Senegal across to Uganda, and grows in parklands where farmers have long conserved it among their fields. It is considered a semi-domesticated tree, protected and managed rather than planted in plantation form.

The genus is named after the Scottish explorer Mungo Park, who described the tree in West Africa. The common name locust bean echoes the European carob, also called locust bean, because the sweet pod pulp resembles carob. Local names reflect the many cultures that use it, including Hausa daddawa, Yoruba iru and Mande soumbala.

Fermented locust bean seasoning has been a staple of West African food for centuries. Women across the Sahel and savanna prepare it in village kitchens, a labour-intensive process of boiling the seeds for hours, removing the hulls, and fermenting the cotyledons. The resulting condiment adds flavour and protein to soups, stews, rice and sauces, and was an essential flavouring in places where meat or fish were scarce or costly.

The tree is valuable in other ways: the sweet yellow pulp provides a sugary snack and drink base, the bark and leaves have medicinal uses, and the tree enriches soil and shades crops. In many regions it has been protected by customary law and cultural taboos.

Food scientists now study locust bean as a source of plant protein, and fermented West African condiments have gained wider attention among chefs and in the African diaspora, who use iru and daddawa as natural flavour enhancers. Overharvesting and tree loss in some regions have raised concerns for the tree's future and for the households that rely on its seasonal income.

Fermented seed cakes are crumbled into soups, stews, rice dishes and sauces across the Sahel and coastal West Africa, including Nigerian egusi and ogbono soups and Burkinabe sauces. The yellow pulp is eaten fresh, mixed with water into a sweet drink, or added to porridge. Unfermented seeds are sometimes roasted as a snack.

Beyond food, the bark, roots and leaves feature in traditional remedies, and the pods and seed coats are used as animal feed, dye and fuel. Cakes are often sold wrapped in leaves or as dried balls, and a small piece is enough to season a whole pot of soup.

Fermented locust bean is a notable plant protein and flavour source, and fermentation improves digestibility and reduces some antinutrients in the raw seed. Research has examined its amino acid profile, and traditional uses include digestive and blood pressure remedies, though clinical evidence for medicinal uses is limited. It is eaten in small amounts as a seasoning, so its nutritional contribution depends on the dish.