Cassava is a staple for hundreds of millions of people in West and Central Africa, and some of its best-known foods are fermented: gari (toasted granules), fufu (a smooth, stretchy dough) and attiéké (a steamed couscous from Côte d’Ivoire). Fermentation isn’t only about flavor here – together with grating, pressing and heat, it’s part of how cassava is made safe to eat.
Why Cassava Has to Be Processed
Raw cassava contains the cyanogenic glycosides linamarin and lotaustralin, which can release hydrogen cyanide (HCN). Traditional processing – peeling, grating, soaking or pressing, fermenting, and roasting or cooking – brings the enzyme linamarase into contact with the glycosides and lets the cyanide escape; making gari this way removes around 80–95% of it (Padmaja, 1995).
International food standards set limits for the finished products: 2 mg/kg of free HCN for gari and 10 mg/kg of total HCN for cassava flour (Codex CXS 193; FSANZ). Codex classes cassava with more than 50 mg/kg HCN (fresh weight) as “bitter” (FSANZ).
Skipping steps has real consequences. Konzo, an abrupt and irreversible paralysis of the legs, is linked to eating insufficiently processed bitter cassava alongside a low-protein diet, typically during food shortages (Nzwalo & Cliff, 2011). In one Congolese community, teaching the “wetting method” – dampening cassava flour and leaving it in a thin layer before cooking – brought flour cyanide below 10 ppm, and no new cases of konzo appeared over the following 18 months (Banea et al., 2012).
Safety Rules for Home Cooks
- Use sweet (low-cyanide) cassava varieties where you can, and buy from a source that knows which variety it is. You can’t measure cyanide at home.
- Never shorten the process. Peel fully, grate finely, ferment for the full time, press out and discard the liquid, and always finish with heat (toasting or steaming or cooking).
- Discard the pressed liquid and soaking water – don’t reuse them in food.
- Throw out any batch that tastes bitter after processing, or that shows mold.
- If in doubt, buy commercially made gari, fufu flour or attiéké, which should meet local food-safety standards.
Gari: Pressed, Fermented and Toasted
The Codex standard describes gari as cassava that is peeled, washed and grated, then fermented, pressed, broken up and granulated, dried if needed, sifted and heat-treated, with a moisture content of no more than 12% (Codex CXS 151). In a study of gari fermentation in Benin, most lactic acid bacteria were Lactobacillus plantarum, Leuconostoc fallax and L. fermentum; L. plantarum acidified fastest and often produced linamarase (Kostinek et al., 2005).
- Peel and wash the roots, then grate finely.
- Pack the mash into a cloth bag and press it under weight for 2–3 days at room temperature, pouring away the expelled liquid. It ferments while it presses and smells pleasantly sour.
- Break up the pressed cake, sieve it into granules, and toast in a wide dry pan over medium heat, stirring constantly, until dry, crisp and light golden (roughly 20–30 minutes per batch).
- Cool completely and store airtight.
Gari is eaten as eba (stirred into hot water to make a firm swallow for soups) or soaked in cold water with sugar, milk and groundnuts. Full recipe: our gari guide.
Attiéké: Fermented and Steamed Cassava Couscous
For attiéké, grated cassava is mixed with about 10% of a traditional fermented cassava starter. In a study of small-scale production, lactic acid bacteria dominated the ferment, starting with Leuconostoc mesenteroides; steaming then cut the remaining bacteria dramatically, and the finished attiéké had a pH of about 4.4 (Coulin et al., 2006).
- Mix finely grated cassava with a little starter (a portion of an earlier ferment) and leave covered for 12–24 hours.
- Press out the liquid, then rub the mash through your hands or a coarse sieve into small granules and let them dry a little.
- Steam the granules until tender and fluffy, fluffing them between two rounds of steaming.
Attiéké is served with grilled fish, onions, tomato and chili – a combination famous in Côte d’Ivoire.
Fufu: Soaked, Fermented and Cooked
For fufu, cassava roots (whole or in pieces) are soaked in water for several days until they soften and sour – a process called retting. During retting the soaking water becomes acidic, and yeasts and lactic acid bacteria break down the roots and help release cyanide. The softened pulp is then sieved, pressed and cooked into a smooth, stretchy dough.
- Peel the roots, cut them into chunks and soak in plenty of clean water for 3–4 days, changing the water daily, until they’re soft.
- Mash and push through a sieve to remove fibres, then let the starch settle and press out the water in a cloth.
- Cook the pulp in a heavy pot, stirring hard, until thick, glossy and elastic. Serve hot with soups and stews.
Related African ferments: ogi (fermented maize porridge) and kunu. Across the Pacific, starchy breadfruit was fermented in pits – see fermented breadfruit.