Though there are several cultivars of cassava out there, most cultures place the different species into one of two broad categories: bitter (sour) and sweet. And as you might expect, the bitterness of a cassava corresponds to the amount of cyanide-producing glucosides it contains, with the bitter ones containing up to 50 times more linamarin than the sweet ones.
Thankfully modern industrial cassava processors have very efficient methods for removing the toxin-creating compounds from their flours, freeing us to consider them for their culinary uses alone. In Brazil, for example, it’s common to see both sweet and sour cassava flours for sale. They’re typically blended by home bakers to achieve the perfect Pão.
I should point out that modern-day science isn’t only looking for newer and better ways to remove toxins from cassava tubers, it’s also trying to create better cassavas, with lower levels of linamarin and higher levels of vital nutrients. Research has been proceeding along these lines in recent years, as poor and/or inadequate cassava processing still causes quite a bit of illness around the world, especially in Africa.
Then again, it’s not just poor cassava processing that causes illness. The act of processing itself can be dangerous, as many sub-Saharan African women know. They are the ones who do most of the cassava mashing, washing and drying, and as a result end up inhaling quite a bit of the cyanide gas that evaporates from the mash. This results in a disease known as konzo, which is essentially low-level cyanide poisoning.