Last updated on October 30th, 2026 at 08:01 pm
Cyanide in cassava flour comes from cyanogenic compounds in the raw root, and badly processed flour can keep far too much of them. Well-made flour falls below the international limit, so processing quality decides almost everything a buyer should check.
Every batch of flour I make starts with thick peeling, washing, and cutting the roots into half-inch cubes.
The cubes then dry in my oven until brittle, and only then does the blender turn them into flour.
Each of those steps exists partly to drive out cyanogenic compounds, not just to make flour.
Here, we explain where the cyanide comes from, what the official limits say, and what testing across Africa has actually found.
It also shows which processing steps remove the most cyanide, and how buyers can choose flour that stays safely under the limit.
Table of Contents
Where the Cyanide Comes From
Cassava roots contain cyanogenic glucosides, mainly linamarin, which release hydrogen cyanide when the root’s cells are damaged.
Bitter varieties carry far more of these compounds than sweet ones, as the guide to bitter versus sweet cassava explains.
An FAO paper on cassava detoxification notes that grating spreads the cyanide evenly through the product, so later steps can remove it.
Flour carries no cyanide of its own beyond what processing leaves behind, which makes the producer’s method the deciding factor.
The Official Limits for Cyanide in Cassava Flour
Codex limits hydrogen cyanide in edible cassava flour to 10 milligrams per kilogram, as FSANZ records in its cassava review.
The same review notes a stricter Codex limit of 2 milligrams per kilogram for garri, the roasted Nigerian staple.
The Codex standard for edible flour also caps moisture at 13 percent, since damp flour stores poorly.
The European Union introduced maximum levels for hydrocyanic acid in cassava and tapioca flour from 2023 under Regulation (EU) 2022/1364.
For whole diets, EFSA set an acute reference dose of 20 micrograms of cyanide per kilogram of body weight.
Does Cassava Flour Contain Cyanide? What Testing Found
A 2025 systematic review in Frontiers in Sustainable Food Systems pulled together data on cyanide in cassava flour and other products from studies across Africa.
Cassava flour averaged 71.1 milligrams per kilogram, and some fermented flour samples reached 200, far above the Codex limit.
Garri averaged only 5.7 milligrams per kilogram, with white and palm oil garri samples testing at zero.
Akpu dough from mid-western Nigeria tested as low as 0.2, showing how thorough soaking and fermenting can work.
Those averages describe market and village samples from poorly controlled processing, not every bag of flour on a shop shelf.
Which Processing Steps Remove the Most
| Processing method | Reported reduction | Final level (mg/kg) |
|---|---|---|
| Peeling, soaking, fermenting, and frying | 100 percent | 1.5 |
| Boiling for 30 minutes | 96.3 percent | 5.1 |
| Fermenting and drying | 80 percent | 10.2 |
| Sun-drying alone | 30 percent | 30.5 |
| Traditional soaking alone | 20 percent | 50.7 |
These figures come from studies compiled in the 2025 review, so they show patterns rather than guarantees.
Combining steps clearly beats relying on drying or soaking alone, which is why good flour makers never skip stages.
The FAO paper adds that soaking removes about 20 percent of free cyanide from fresh chips after four hours.
It also reports that sun-dried cassava kept only 10 to 30 percent of its original cyanide in one cited study.
Full home methods are set out in the guide to removing cyanide from cassava.
Production routes, from the fermentation method to the industrial method, each handle cyanide differently.
How I Keep My Flour Safe
I remove both the brown skin and the thick inner layer, because the peel holds much of the cyanide.
The peeled roots get one basin wash and a single rinse in borehole water before cutting.
Small half-inch cubes dry evenly, and I keep them in the oven until they show uniform color and snap cleanly.
Every batch then passes through three sieves, giving fine, dry flour that stays in good condition for months.
How to Buy Safe Cassava Flour
- Check the processor: buy from brands or producers who explain their peeling, drying, and testing methods.
- Look for test results: reputable suppliers can share cyanide results showing levels below 10 milligrams per kilogram.
- Taste a pinch: flour that tastes clearly bitter may come from poorly processed bitter roots, so avoid it.
- Check dryness: flour should feel dry, smell neutral, and pour freely without clumps or sourness.
US shoppers can compare tested brands in the guide to the best US flour brands.
The quick-dried, unfermented grade preferred by industry is explained in the guide to high quality flour (HQCF).
Related Health Risks
Long-term intake of poorly processed cassava is linked to konzo, a paralytic disease covered in the article on konzo disease.
Acute symptoms and emergency signs are described in the guide to cyanide poisoning from cassava.
The amounts involved in serious harm are discussed in how much cassava can kill you.
Other contaminant questions are reviewed in the article on flour and lead poisoning, and the cassava flour pillar links every related topic.
Conclusion
Cyanide in cassava flour comes from raw roots carrying cyanogenic compounds that only careful processing removes.
Codex sets 10 milligrams per kilogram for flour and 2 for garri.
A 2025 review found poorly processed African flour averaging 71.1, while combined peeling, soaking, fermenting, and cooking cut levels close to zero.
Buy from processors who peel thoroughly, dry completely, and can share test results.
My routine of thick peeling, small cubes, and slow oven drying follows that same logic.
For oven-dried, triple-sieved flour from Ntigha, message Cassava Pathway directly on WhatsApp.
Frequently Asked Questions
Is all cassava flour safe to eat?
Well-processed flour that meets the Codex limit of 10 milligrams per kilogram is considered safe.
Poorly processed flour from unknown sources can exceed that limit many times over.
What is the official cyanide limit for this flour?
Codex sets a maximum of 10 milligrams of hydrogen cyanide per kilogram.
The stricter Codex limit for garri, the roasted Nigerian staple, is only 2 milligrams per kilogram.
Does cooking remove any remaining cyanide?
Cooking helps, since studies compiled in one review found 30-minute boiling cut levels by 96.3 percent.
Safe flour still depends mainly on processing long before it reaches you.
How can I tell if flour was processed safely?
Choose producers who explain their peeling and drying, and always ask for cyanide test results.
Avoid flour that tastes clearly bitter, smells sour, or feels damp and clumpy.
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 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.