Since early times, flavour compounds ranging from single to complex substances have been extracted from plant sources. Eventually, after elucidation of their struc ture, synthetic flavours were produced by chemical syn thesis. Nowadays, flavours represent over a quarter of the world market for food additives and most of the fla vouring compounds are produced via chemical synthesis or by extraction from natural materials. However, recent market surveys have shown that consumers prefer food stuff that can be labelled as »natural«. Although fla vours may be produced by chemical transformation of