Mixing cassava flour samples with water and standing in the sun for 2 hours or in the shade for 5 hours, gives a 3-6 fold reduction in cyanide content (Bradbury, 2006; Cumbana et al., 2007; Bradbury and Denton, 2010a). Water rapidly swells the flour and allows contact between linamarin and the enzyme linamarase that catalyses breakdown of linamarin to acetone cyanohydrin, which then breaks down spontaneously to hydrogen cyanide gas. The amount of hydrogen cyanide lost from the flour increases as the amount of linamarase is increased. The method is a gift from God.

The simple wetting method is as follows:

A bowl is filled with cassava flour and a mark made on the inside of the bowl. Water is added with mixing until the wet flour comes up to the same mark. The wet flour is spread in a thin layer not more than the depth of a fingernail on a basket and left in the sun for 2 hours or in the shade for 5 hours for hydrogen cyanide gas to escape. The wet flour is mixed with boiling water as is the custom, to produce a stiff porridge.

The wetting method was field tested in Mozambique in 2005 and rural women readily accepted it. The method does not require additional equipment or cause more work. Most people preferred the taste of the thick porridge (ugali) made from treated flour, because it had lost the bitter taste due to linamarin present in the ugali made from untreated flour (Muquingue et al., (2005), CCDN News No 6, p 3-4; Nhassico et al., 2008) The wetting method is now being widely taught and has been endorsed by the Ministry of Health in Mozambique (Cliff et al., 2011).

Dr Dulce Nhassico produced an illustrated poster in Portuguese explaining konzo and the wetting method, which has been modified to include cyanide poisoning (Bradbury et al., 2011). The coloured, laminated poster is now available for free in 13 different languages (see Posters available on konzo, cyanide poisoning and wetting method). In 2008-9 we carried out a program, supported by AusAID, of rehabilitation of konzo subjects in Tanzania and the wetting method was taught to 216 women from konzo-prone villages in southern Tanzania (Mlingi et al., 2011). In DRC we are working to prevent further cases of konzo in a village with 34 konzo subjects by teaching the wetting method to the mothers, who are nearly all using it on a routine basis (see Prevention of konzo using wetting method in a village in DRC).