Bambara groundnut

Bambara groundnut is a low, bushy, spreading legume with trifoliate leaves. After flowering, the stalks bend down and push the young pods into the soil, where each pod matures with one or two seeds, much as peanuts do.

The mature seeds are round to slightly oval, about the size of a large pea or small chickpea, and extremely hard when dry. The coat may be cream, brown, red, black, or mottled, often with a darker eye.

The flavour is earthy and slightly sweet, reminiscent of a cross between peanut and pea. The seeds are sold dried, boiled and canned, parched, or ground into flour.

The crop is native to West and Central Africa, and the wild forms are known from the region around northern Nigeria and Cameroon. It has been cultivated there for centuries, and it spread across the continent and to Madagascar and, in small amounts, to Asia and the Americas.

The English name comes from the Bambara people of the Niger River area in Mali, with whom Europeans first associated the crop. Nearly every African language has its own name for it.

The species was earlier placed in the genus Voandzeia, and that older name survives in French common names such as voandzou.

Bambara groundnut has been grown by African farmers mainly for household use, often by women, as an intercrop with cereals, because it fixes nitrogen, tolerates heat and poor soil and yields something even in dry years. It has therefore been called an orphan or neglected crop by international agencies, even though it is the third most important legume in parts of sub-Saharan Africa after peanut and cowpea.

Colonial-era agronomists noticed the crop in the 18th and 19th centuries and some records show it in the Caribbean and Brazil, probably through the slave trade.

Traditional processing includes long boiling, pounding into flour for steamed puddings, and fermenting. Several cultures treat the seed as a food of fertility or good luck.

Since the early 2000s research bodies including the Crop Trust and African national programmes have promoted it as a climate-resilient crop, and breeding and seed saving projects have collected hundreds of landraces. Interest in plant-based protein has also drawn attention to it in urban markets and in food science labs.

Seeds are boiled and eaten whole, often with oil, salt and pepper, or ground into flour for a steamed bean pudding known as okpa in southeastern Nigeria and as other local dishes elsewhere. Fresh immature seeds can be boiled like green peas or roasted in the pod.

Dried seeds may be soaked, dehulled and made into porridge, stews, fritters or a milk-like drink. Their hardness means they need long soaking and cooking.

The flour is increasingly tested in gluten-free baking and snack products. Plants and haulm are also fed to livestock.

Bambara groundnut seeds supply protein, complex carbohydrate and fibre, plus useful minerals such as iron and zinc, though the amounts available to the body depend on how the seeds are processed. Soaking, cooking and fermenting reduce anti-nutritional compounds such as phytates and tannins.

Because it is a pulse, regular intake is consistent with the benefits associated with other legumes, such as help with satiety and steady blood sugar. Direct clinical trials on the seed are very limited.