Analysis and Survey of Cyanogenic Glucoside (as Hydrogen Cyanide) in Bean Paste by Enzymatic Assay

Abstract

A method for the determination of cyanogenic glucoside in bean paste (nama an) used in Japanese cakes was established by enzymatic assay. The sample was adjusted to pH 5.0 with citrate buffer and incubated with 2 units of the enzyme (linamarase) for 3 hours. The cyanogenic glucoside was thus hydrolyzed to free cyanide, which was estimated, after steam distillation, by the pyridine-pyrazolone method. The enzyme was obtained by ammonium sulfate fractionation of the aqueous extract from butter beans.
The detection limit by this procedure was 0.3ppm linamarin (as hydrogen cyanide) in bean paste. The recovery of linamarin added at 20ppm (as hydrogen cyanide) to the bean paste was more than 92%.
A survey of commercial bean paste by the use of the presented method revealed levels of 0.3 to 97ppm (as hydrogen cyanide) in 46 out of 115 samples. The presented method is believed to be suitable for the quantitative determination of residues of naturally occurring cyanogenic glucoside in bean paste.