Varietal diversity and processing effects on the biochemical composition, cyanogenic glucoside potential (HCNp) and appearance of cassava flours from South-Eastern African region

Abstract

Changes in biochemical quality and cyanogenic safety in flours from different cassava varieties grown within the South-eastern African region as influenced by processing technique were investigated. Two local (Mweulu and Tanganyika) and four improved Cassava Mosaic Disease (CMD)-tolerant cassava varieties (Chila A, Chila B, Bangweulu and Kampolombo) were processed using different processing techniques (chipping, grating and soaking). Flours obtained from these products were studied for changes in their starch content, total, reducing and non-reducing sugars, colour and cyanogenic potential (HCNp) using standard analytical methods. The results showed that the different processing techniques had only minimal but significant (p<0.05) effects on the starch and sugar content of the different cassava varieties. Flour made from chips from all six cassava varieties had relatively high cyanogenic potentials with values ranging between 30.1 mg HCN/kg in Chila A to 64.3 mg HCN/kg in Bangweulu. Grating and soaking of the roots, however resulted in drastic reductions in the levels of the cyanogenic glucosides in all the varieties. The high HCNp levels in the chips from Chila A and Bangweulu were reduced to 16.2 and 13.5 mg HCN/kg by the grating and soaking treatments respectively. Similar reductions in HCNp levels were noted for all the other varieties. Likewise, grating and soaking also caused significant (p<0.05) increase in the L*-values of the cassava flours compared to the cassava chip flours. Soaked Kampolombo had the highest L*-value of 78.40 suggesting that the soaked Kampolombo cassava sample was whiter than the rest of the samples. These findings have implications for the preference and adoption of cassava varieties where the colour of the flour is deemed to be important for the preparation of preferred dishes