Amygdalin

A cyanogenic glycoside concentrated in bitter almonds: when the kernels are crushed or chewed, endogenous enzymes hydrolyse it in the presence of water, releasing hydrogen cyanide and benzaldehyde. The benzaldehyde gives the characteristic marzipan-like aroma of bitter almond; the cyanide is acutely toxic, which is why bitter almonds, apricot kernels and related seeds are regulated and must be detoxified before use. Properly processed kernels yield bitter almond oil, flavourings and persipan — the apricot-kernel alternative to marzipan. Sweet almonds contain only traces, but the bitter varieties demand strict processing controls.