Hydrogen cyanide in plant material

A number of plants and their fruits, e.g. apricot and plum kernels, grape and apple seeds, are natural sources of HCN. The origin of the HCN is a cyanoglucoside, amygdalin (a sugar derivative) which is present in the fruit stones and seeds; hydrolysis of amygdalin releases HCN. Cassava is an important root crop grown in tropical regions as a source of starch, and, for example, it is used for the production of tapioca. Cassava plants may be either a sweet or bitter variety; bitter cassava contains larger quantities of cyanoglucosides which liberate HCN when the roots are crushed or chewed. In order to render the root crop safe as a foodstuff, bitter cassava must be subjected to careful treatment of shredding, pressure and heat. A beneficial side-effect is the natural defence that cassava has against, for example, insect pests.