How to Remove Cyanide From Cassava: Soak, Ferment, Boil, Dry

Last updated on October 30th, 2026 at 08:12 pm

Learning how to remove cyanide from cassava matters because raw roots carry compounds that release a poison when cells break.Peeling, soaking, fermenting, boiling, and drying can each cut those compounds, and combining them works better than any single shortcut.

In my community in Nigeria, where cassava is eaten daily, nobody was ever explicitly taught that processing removes the toxins in the roots.

Nobody even tried eating cassava raw, since even a small taste sends you running to the toilet.

The safety steps were simply built into the culture, passed down through families without anyone calling it food safety.

This article pairs those household methods with published research on how much cyanide each step actually removes.

It covers peeling, soaking, fermenting, boiling, and drying, then explains why combining steps matters and what happens when a batch skips one.

Why Cassava Needs Processing

Cassava roots contain cyanogenic glucosides, mainly linamarin, which release hydrogen cyanide when the root’s cells are crushed or cut.

Bitter varieties carry far higher levels than sweet ones, as the guide to bitter versus sweet cassava explains.

Codex limits finished flour to 10 milligrams of hydrogen cyanide per kilogram and garri to 2, as FSANZ records.

Basic facts about the root itself are covered in the guide asking what cassava root is.

Every household that wants to remove cyanide from cassava relies on some mix of the five steps below.

Step 1: Peel Thoroughly

Our knives lift the brown skin and the thick inner rind together, leaving only clean white flesh behind.

That inner layer matters, because the peel holds much of the root’s cyanogenic content.

We peel first and wash afterward, then cut the flesh smaller so water and heat reach every part.

Knife techniques that limit waste appear in the guide on how to peel cassava root.

Step 2: Soak, and Change the Water

An FAO paper on cassava detoxification found that four hours of soaking removed only about 20 percent of free cyanide from fresh chips.

The same paper says bound cyanide barely moved in that time, while changing the water over three to five days gave a much larger reduction.

Professor Oke of the University of Ife reported soaked chips falling from 108.2 to 2.9 parts per million after five days, according to ISTRC proceedings.

For akpu, we soak roots in a drum or basin for three days in strong sun, or four when the weather stays cloudy.

Akpu and its regional cousins are compared in the article on what fufu is.

Step 3: Ferment Grated Mash

Grating spreads the cyanogenic compounds evenly through the mash, the FAO paper notes, and longer fermentation lowers what remains.

Our garri mash sits under a press for a full day, then gets sieved and roasted on the third day.

If roasting slips to a fourth day, the mash turns unpleasantly sour, so we keep that schedule strictly.

A 2019 study in Scientific African measured cyanide elimination of about 80 percent for garri and 91 percent for fufu.

Oke also found garri fried with palm oil usually carried no detectable cyanide, while unoiled garri held 5 to 20 parts per million.

The full process is in the garri production guide, with grating covered under using grated cassava.

Step 4: Boil and Discard the Water

Boiling breaks down free cyanide quickly, and the water must always be thrown away afterward.

Oke found that 15 minutes of boiling removed over 90 percent of free cyanide from chips.

A 2025 systematic review in Frontiers in Sustainable Food Systems lists 30 minutes of boiling cutting levels by 96.3 percent.

Ngwa households rarely boil cassava to eat directly, but we boil roots half done when making abacha.

The boiled slices then soak overnight and dry in the sun for three or four days until hard.

Cooking the root as a meal is covered in the guide to boiled cassava root.

Step 5: Dry Completely

The FAO paper reports that sun-dried cassava kept only 10 to 30 percent of its original cyanide in one cited study.

It adds that proper sun-drying takes one to three days in the dry season, and up to eight in the rainy season.

Other studies show weaker results, and the 2025 review lists sun-drying alone at just 30 percent reduction.

For my flour, half-inch cubes dry in the oven on low heat until they show uniform color and snap cleanly.

Drying methods and equipment are compared in the guide to cassava drying techniques.

Best Ways to Remove Cyanide From Cassava, Compared

Results vary widely between studies, varieties, and conditions, so treat every figure as a guide rather than a guarantee.

The pattern holds firm, though, because combined steps consistently beat any single method used alone.

What Happens If You Skip a Step

Long-term intake of poorly processed cassava is linked to konzo, a paralytic disease covered in the article on konzo disease.

A single badly processed batch can also cause acute illness, described in the guide to cyanide poisoning from cassava.

The doses involved in serious harm are discussed in how much cassava can kill you.

Shop-bought flour has its own limits and test data, set out in the post on cyanide in cassava flour.

Every household method is described in full in the guide to traditional methods of processing cassava.

Conclusion

Knowing how to remove cyanide from cassava comes down to combining steps rather than trusting one shortcut.

Peel away the inner rind, soak with frequent water changes, ferment grated mash, boil and discard the water, then dry completely.

Whatever the dish, throw away every drop of soaking and boiling water.

Research shows five-day soaking, garri processing, and 30-minute boiling each removing most cyanide.

Ngwa households still follow these steps daily for akpu, garri, and abacha.

For cassava processing questions or carefully made flour from Ntigha, message Cassava Pathway on WhatsApp.

Frequently Asked Questions

How long should cassava be soaked to remove cyanide?

Four hours removes only about 20 percent of free cyanide, so soak three to five days.

Change the water regularly, because fresh water keeps drawing out released compounds.

Does boiling alone remove enough cyanide from cassava?

Boiling removes most free cyanide, with one study reporting 96.3 percent after 30 minutes.

Bitter varieties still benefit from peeling, soaking, or fermenting before they are finally cooked.

Is fermentation necessary if I already boil cassava?

Sweet varieties are usually safe when peeled and boiled thoroughly, but bitter varieties need much more.

Fermentation, as in garri and akpu, adds a powerful extra reduction step.

Can I reuse the water from soaking or boiling cassava?

No, that water holds the cyanide compounds released from the roots during processing.

Pour it well away from drinking water sources, livestock, and young children every single time.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. The author is not a medical doctor or registered dietitian. Always consult a qualified healthcare provider before making dietary or medical decisions related to cassava consumption.

Chimeremeze Emeh

Chimeremeze Emeh is a tropical crop farmer and chemical engineer from Ntigha, Isiala Ngwa North LGA, Abia State, Eastern Nigeria, specializing in cassava and palm oil, with over 30 years of hands-on experience growing, harvesting, and processing cassava. He grows TMS series, TME 419, and local traditional varieties on his own farms and operates a small-scale cassava flour and starch production business through Cassava Pathway, which he founded as a CAMA-registered agribusiness in 2024. He is also the founder of Palm Oil Pathway, where he applies the same tropical farming expertise. His farms are located in Ntigha, Abia State.