NMR Spectroscopy: A Powerful Tool to Investigate the Role of Tannins in the Taste of Wine and their Health Protective Effect
Pp. 188-221 (34)
Julie Géan, Aurélien L. Furlan, Olivier Cala, Marie-Lise Jobin, Aurore Castets, Cécile Simon, Isabelle Pianet and Erick J. Dufourc
Tannins in the skin and seeds of grapes used to make red wine are
responsible for the two dominant sensory perceptions of astringency and bitterness.
Astringency is a tactile sensation causing a dry, rough and puckering mouth-feel, while
bitterness triggers an unpalatable harsh taste. Although these flavors are both associated
with tannins, their mechanisms of action differ greatly. Astringency results from an
interaction between the tannins and the saliva proteins, whereas bitterness is the result
of an interaction between the tannins and the taste receptors located on the tongue. In
the last decade, various studies using NMR spectroscopy have revealed new clues to
the understanding of astringency perception at the molecular level. We now know the
three-dimensional structure and the colloidal state of tannins are key factors in the mechanism of tannin-saliva protein interactions. Although the latter are undeniably
related to astringency, it is only very recently we have learned that the lipids of oral
cavity membranes and a fortiori provided by fat foods could also play a role in this
complex sensory phenomenon. Indeed, strong interactions between tannins and
membrane lipids have been highlighted in recent research supported by a fluidizing
effect on membranes depending on the tannin structure. These findings show lipids
interfere with tannin-saliva protein and tannin-taste receptor interactions involved in
astringency and bitterness respectively. In addition to their role in taste, tannins as
antioxidant molecules and in a larger extent polyphenolic compounds provided by
foods are strongly suspected to have a positive role in many pathologies. Whereas their
antioxidant properties have been widely demonstrated, their protective effect on
membrane against lipid oxidation has been shown for the first time by NMR
investigations. New insights into the location of tannins within the membrane have
been proposed to explain their inhibitory effects on free radicals. Moreover, a
synergistic effect has been evidenced proving the beneficial effect of food polyphenols
as shown by epidemiological studies.
Antioxidants, Astringency, Bitterness, Lipid oxidation, Membrane
location, Molecular dynamics, NMR, Polyphenols, Synergistic effect, Tanninlipid
interactions, Tannin-saliva protein interactions, Taste, Wine tannins.
Institute of Chemistry and Biology of Membranes and Nano-objects, UMR 5248, Univ. Bordeaux, CNRS, Bordeaux INP, F-33600, Pessac, France.