1981 Volume 28 Issue 8 Pages 412-417
A modified enzymatic method for assaying cyanide content of butter beans (Phaseolus lunatus L.) imported from Burma for "Ann" manufacture was descrived. To liberate HCN from its glycosides, the enzyme was extracted from powder of the beans with M/10 citrate buffer (pH 6.0). The cyanogenic glycosides in dry beans, as well as soaked ones, were extracted with 80% ethanol under reflux, and treated with the enzyme to liberate HCN which was estimated spectrometrically after distillation. The inherent free HCN was estimated after distillation with acids without the enzymatic treatment. Results obtained were as follows: 1) The optimum conditions for the enzymatic assay were 50°C, pH 5.5. 2) When the mixture of enzyme and extract containing cyanogenic glycosides from beans was incubated at 50°C for 1.5hr, 89.1% of the glycosides was recovered. 3) Fifty percent or more of the cyanogenic glycosides was remained intact in beans during soaking in water at 20°C for 18hr or 50°C for 4hr. 4) Commercial enzymes containing various types of glycosidase had no liability for liberation of HCN from cyanogenic glycosides. A little HCN was liberated from the glycosides by treating with mineral acids at 40°C. HCN equivalent to about 50% of the glycosides was liberated by boiling with 1N HCl for 1hr.
