An enzymatic assay for the total cyanide content of cassava (manihot esculenta crantz)

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Abstract
An enzymatic assay for the cyanide contents of cassava parenchymal tissue (peeled root), cassava peel or cassava leaves is described. The material is homogenised in orthophosphoric acid; filtered through glass‐fibre paper and aliquots of the filtrate are neutralised and incubated with exogenous linamarase for 15 min. The cyanogenic glucosides present are hydrolysed to free cyanide which is estimated spectrophotometrically. The acid extraction solution inactivates endogenous linamarase, and assay of aliquots without enzyme treatment gives the free (non‐glycosidic) cyanide contents of the extracts. The acid extracts are stable for at least 4 days at 4°C, and the steam‐distillation/aspiration of earlier methods is unnecessary. The detection limit is < 0.01 mg (0.1 parts 10−6) cyanide per 100 g fresh weight and peeled root, and 40‐50 samples per day can be handled easily. Analyses of eight cultivars indicated longitudinal and radial cyanide gradients in the roots, and the problem of sampling bulky roots is discussed.