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Cassava contains natural compounds that release cyanide when the root is cut or crushed. Traditional steps such as peeling, grating, soaking, fermenting, pressing and drying let the poison escape and make this staple safe to eat.

Cassava

FoodScience

The story behind the card

Cassava was domesticated in South America, probably in the southern Amazon basin, and Portuguese traders took it to Africa in the sixteenth century; today it is a staple for hundreds of millions of people in the tropics. The trouble comes mainly from a compound called linamarin: once the root's cells are damaged, an enzyme in the root breaks it down and hydrogen cyanide gas is released. 'Bitter' varieties contain far more than 'sweet' ones, which is why methods differ. Grating and soaking bring the enzyme and the compound together; fermenting, pressing and sun-drying let the cyanide escape. When food is short and processing is rushed, people can fall ill: konzo, a disease that causes lasting weakness in the legs, has been linked to poorly processed bitter cassava.

Türkçe oku
Manyok, kökü kesilince ya da ezilince siyanür açığa çıkaran doğal bileşikler içerir. Soyma, rendeleme, suda bekletme, fermente etme, sıkma ve kurutma gibi geleneksel yöntemler bu zehrin uçup gitmesini sağlar ve kökü güvenle yenir hâle getirir.

Manyok Güney Amerika'da, büyük olasılıkla Amazon havzasının güneyinde evcilleştirildi; 16. yüzyılda Portekizli tüccarlar onu Afrika'ya götürdü. Bugün tropik bölgelerde yüz milyonlarca insanın temel besinidir. Sorunun kaynağı başta linamarin adlı bileşiktir: kökün hücreleri zarar görünce kökteki bir enzim bu bileşiği parçalar ve siyanür gazı açığa çıkar. “Acı” çeşitlerde bu bileşik “tatlı” çeşitlerdekinden çok daha fazladır; yöntemlerin farklı olması bundandır. Rendeleme ve ıslatma, enzimle bileşiği buluşturur; fermente etme, sıkma ve güneşte kurutma da siyanürün uçmasını sağlar. Yiyeceğin kıt olduğu dönemlerde işlem aceleye getirilirse insanlar hastalanabilir: bacaklarda kalıcı güçsüzlüğe yol açan konzo hastalığı, iyi işlenmemiş acı manyokla ilişkilendirilmiştir.

Sources and further reading

Background reading: Cassava
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