MECHANISM OF CYANOGEN REDUCTION IN CASSAVA ROOTS DURING COOKING

The cyanogen elimination profile during cooking of cassava roots was i nvestigated and correlated with the changes in cyanogenic beta-glucosi dase (GLase) activity monitored at close intervals in the cook water a nd root. Cyanogenic beta-glucosidase (GLase) activity was detected in the cook water within 5 min of starting cooking. Whilst significant de crease in the GLase activity was noticed in cook water and root within 15 and 10 min, respectively, for varieties M4 and H165, H1687 GLase a ctivity decreased tremendously only at 20 and 15 min in the cook water and root, respectively. There was no GLase activity in cook water aft er the 30 min pre-boiling phase while GLase activity was present in th e roots even after 60 min of cooking. The decrease in GLase activity a t 15-20 min preboiling phase led to accumulation of cyanogens in cook water. The cyanogen fractions (glucosidic and non-glucosidic) increase d significantly with cooking in the cook water in the case of varietie s M4 and H165 while their levels were almost static throughout the pos t-boiling phase for H1687. The amount of HCN escaping through steam di d not bear a direct relationship with the initial cyanogen content in cassava roots. Although free cyanogen is highly volatile, all of it do es not escape through steam and a certain quantity appears to be stabi lised in the cook water.