# Cyanogenic glycosides and HCN

I'm researching cyanide for a biology project and noted that one of the largest sources of carbohydrates in the tropics is the cassava root -- which I previously researched as a food that contains a cyanogenic glycoside that is metabolized into hydrogen cyanide.

Most of the sources I reviewed claimed that, while boiling the cassava, the cyanogenic glycosides were broken down into components such hydrogen cyanide, which made the plant safer to consume. I have a limited understanding of chemistry and can't resolve why this is considered a safe way to cook the plant.

My research indicates that inhalation of hydrogen cyanide is significantly more toxic than the oral route, so why would this method be considered beneficial? Not sure why this is considered safer, unless the information I've found is not correct. Any help in putting this together would be appreciated. Thanks!

OK, I was too lazy to look up LD50 and LC50 of $$\ce{HCN}$$ for you ;)

But if you have a chance, have a look at

G. Padmaja & Keith H. Steinkraus,
Cyanide detoxification in cassava for food and feed uses, Critical Reviews in Food Science and Nutrition, 1995, 35(4), 299-339 [DOI]

Seemingly, the processing of cassava (manioc) involves several steps, such as drying in the sun, grating, watering and cooking, each of which either facilitates the enzymatic or thermal cleavage of the linamarin (i.e. the toxic compound) to glucose or supports the release of $$\ce{HCN}$$.

In total, the processing minimizes the risk of exposition through inhalation. None of the steps is perfomed in confined space, watering helps to wash out the $$\ce{HCN}$$ which in water dissociates a bit ($$\ce{HCN}$$ is a weak acid).

Thus, digestion of the untreated roots is likely to be fatal, while the slow processing is apparently not.

Ok, I digged a bit and maybe you have you have access to this one:

Bala Nambisan

Strategies for elimination of cyanogens from cassava for reducing toxicity and improving food safety Food and Chemical Toxicology, 2011, 49, 690–693 [DOI]