Study of wine tannin oligomers by on-line liquid chromatography electrospray ionization mass spectrometry

Thiolysis of a wine tannin fraction yielded trihydroxylated flavanol units (as previously observed in grape skins) in addition to the well-known procy anidins (dihydroxylated units), usually described in the literature for gra pe condensed tannins. To determine how they occur in condensed tannins, the wine fraction was analyzed by liquid chromatography coupled to electrospra y ionization mass spectrometry. Thus, various series of ion peaks containin g a variable number of trihydroxylated units were detected as monocharged i ons from dimers up to pentamers. From pentamers, oligomers were found as do ubly charged ions. Heptamer species corresponded to the highest mass detect ed. These results showed that wine condensed tannins consist of, besides pr ocyanidins, mixed tri- and dihydroxylated flavanol units and also of pure t rihydroxylated flavanol units. These new data should be taken into account to interpret organoleptic properties of wines.