STUDIES ON THE QUANTIFICATION OF SPECIFIC CYANOGENS IN CASSAVA PRODUCTS AND INTRODUCTION OF A NEW CHROMOGEN

The enzymic assay for cyanogens in cassava as developed by Cooke (1978) and improved by O'Brien et al (1991), was compared with a standard method, involving autolysis/steam distillation/titration, and further improved with a more acceptable coloration and other minor changes. Cooke's assay, using a linamarin calibration curve, gave similar values for cyanogenic potential in fresh cassava as the standard method. For cassava samples with high non-glycosidic cyanogen levels, Cooke's assay yielded slightly lower values. Isonicotinate/1,3-dimethyl barbiturate as reagent in the Konig reaction had the following advantages compared with the so far applied pyridine/pyrazolone color reagent. It is less toxic and does not release repulsive vapours. It is faster, cheaper and easier to handle, and has increased sensitivity and longer storability. Direct measurement of cyanogenic potential was accurate in extracts containing 35-700 muM. Recovery of linamarin supplements was 102 +/- 4%. Separate calibration curves of linamarin, acetone cyanohydrin and KCN were necessary for accurate calculation of cyanogenic glycosides and cyanohydrin levels. Extract storability depended slightly on storage temperature, but was not changed by inclusion of ethanol in the extract medium.