Dr Edward Mutandwa
Dr Julie Cliff, who has sent you some material on processing of cassava leaves, has suggested that I send you results of our experience on processing to remove cyanide compounds from cassava flour and cassava leaves.
1. Cassava flour.
The wetting method that we developed for removing cyanogens from cassava flour is very simple as follows:
Cassava flour is placed in a basin and the height of the flour is marked on the inside of the basin. Water is added with stirring and the volume of the flour decreases and then increases again as more water is added, until it comes up to the mark on the basin. The wet flour is then spread in a thin layer not more than 1 cm deep on a mat or basket and left in the shade for 5 hours or the sun for 2 hours, which allows the enzyme linamarase to break down the linamartin to hydrogen cyanide gas, which escapes through the thin layer of flour. The damp flour is then used to make the thick porridge called ugali in East Africa and fufu in DRC. The method has been used for 3 years in DRC and is being used in DRC to control konzo, see attachment, and is being used in Mozambique in a collaborative project with Dr Julie Cliff. The fufu is as good as that made from chickwangue. It tastes much better due to removal of bitter linamarin and stores better than fufu made from untreated flour, and best of all the women like using the wetting method. Its use is spreading from one village to another by word of mouth.
2. Cassava leaves.
The current method of grinding the leaves followed by boiling for at least 30 min removes all the cyanogens from the leaves, but unfortunately the prolonged boiling also removes many of the vitamins and some amino acids from the protein rich leaves. We are still working on methods for removing the cyanogens from cassava leaves either at room temperature or at a temperature of 50 degrees C, see attachment. Our best published method is to pound the leaves for 10 min followed by washing the leaves in water at ambient temperature. The total cyanide content of the pounded, washed leaves is reduced to 8% after two washes and 3% after a total of 4 washes. This process removes virtually all the cyanogens from pounded cassava leaves without breaking down the vitamins and protein present in the leaves.
Control of konzo in DRC using the wetting method on cassava flour
Mild methods of processing cassava leaves to remove cyanogens and conserve
I hope that you may be able to include this submission in your Global Forum, even although it is submitted just before your deadline.
With best wishes.
Dr Howard Bradbury.
Links and resources:
Indigenous Peoples’ food systems: the many dimensions of culture, diversity and environment for nutrition and health
Comparative Assessment of Indigenous Methods of Sweet Potato Preservation among Smallholder FArmers: Case of Grass, Ash and Soil based Apporoaches in Zimbabwe
FSN Forum discussion: Looking back to effective rural practices ... Did we miss something?