Since early times, flavour compounds ranging from
single to complex substances have been extracted from
plant sources. Eventually, after elucidation of their structure,
synthetic flavours were produced by chemical synthesis.
Nowadays, flavours represent over a quarter of
the world market for food additives and most of the flavouring
compounds are produced via chemical synthesis
or by extraction from natural materials. However, recent
market surveys have shown that consumers prefer foodstuff
that can be labelled as »natural«. Although flavours
may be produced by chemical transformation of natural substances, the resulting products cannot legally
be labelled as natural. Furthermore, chemical synthesis
often results in environmentally unfriendly production
processes and lacks substrate selectivity, which may cause
the formation of undesirable racemic mixtures, thus reducing
process efficiency and increasing downstream
costs. On the other hand, the production of natural flavours
by direct extraction from plants is also subject to
various problems. These raw materials often contain low
concentrations of the desired compounds, making the
extraction expensive. Moreover, their use depends on
factors difficult to control such as weather conditions
and plant diseases. The disadvantages of both methods
and the increasing interest in natural products have directed
many investigations towards the search for other
strategies to produce natural flavours.