Pigments in wine

Cameira dos Santos, J.P. et al., Detection and partial characterization of new anthocyanin-derived pigments in wine. J. Sci. Food Agric. 70, 204, 1996. 

Calculation of the theoretical levels of anthocyanins and tannins in wines is possible, assuming complete extraction of these compounds from the parts of the cluster. Thus one sees only 20-30% of the possible grape pigments in wine. 

Table 2.5 HPLC gradient program used for analysis of polymeric pigments in wine using a polystyrene divinylbenzene (100 A, 250 x 4.6mm, 5 pan) column (flow rate l.OmL/min) (Peng et al., 2002).

Figure 3.19 A method for fractionation of oligomeric pigments in wine (Asenstorfer et al., 2001)...

Finally, the relative amounts of anthocyanin-flavanol pigments and anthocyanin-anthocyanin pigments obviously depend on the anthocyanin to flavanol ratio. However, the kinetics of anthocyanin polymerization and flavanol-anthocyanin reactions as well as the quantities of the resulting pigments in wine remain to be established. Consequently, the importance of these processes with respect to other anthocyanin reactions (hydration and subsequent degradation, cycloadditon with yeast metabolites) and the impact of resulting polymeric anthocyanins on wine quality are speculative. 

Ethyl-linked pigments in wine-like media are also short lived. Francia-Arichia et al. (13) showed that ethyl-linked procyanidin B2-Mv dimers at pH 3.2 in a model solution reached a maximum after 10 days but then declined to negligible levels after 120 days. The rate constants for the formation and disappearance of ethyl-linked pigments formed from other procyanidins show... 

Recent advances in mass spectrometry allow for the characterization of complex mixtures of anthocyanin-polyflavan-3-ol pigments in wine... 

The routine analysis of polymeric pigments in wine is based on the work of Somers who showed that monomeric anthocyanins are bleached with bisulfite whereas polymeric pigments are not (i,5). Thus, the difference in absorbance readings at 520nm before and after bleaching with bisulfite is widely used as a measure of the amount of polymeric pigment present in red wine. 

Figure 1 shows the scheme we currently use for the parallel determination of tannin and polymeric pigments in wines and berry extracts. The boxed branch... 

Johnson, T.V. and Morris, J.R. 1996. Separation of anthocyanin pigments in wine by low pressure column chromatography. J. Food Sci. 61, 109-111. 

Compared with other pigments in wine, these new molecules are present in very small quantities. 

F-A pigments are described to result from the direct condensation between anthocyanins and condensed tannins (proanthocyanidins). The presence of these pigments in wines was confirmed recently (Salas et al, 2004a). Their formation mechanism was described to involve two fundamental steps (see Fig. 3.9) first, the acid-catalyzed cleavage of inter-flavan linkage of proanthocyanidins, yielding a carbocation in C-4 and then, the carboca-tion may react on the nucleophilic position C-8, or less likely the C-6, of the hemiacetal form of anthocyanin to form the F-A adduct. 

Once again, the detection of these pigments in wines reinforces the importance of acetaldehyde as an intermediary in the chemical transformations that occur in red wine during aging, leading to the color change. 

Applying the Science 11.1 discusses the polymerization of pigments in wine. 

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