Wine Chemistry and Biochemistry

9D Influence of Phenolics on Wine Organoleptic Properties 549

Wavelength

pH 1.0

pH 1.5

pH 2.0

pH 2.4

pH 3.0

pH 4.0

250 300 350 400 450 500 550 600 650 700

0

0.2

0.8

1.0

0.4

0.6

1.2

Wavelength (nm)

pH 1.0

pH 1.5

pH 2.0

pH 2.4

pH 3.0

pH 4.0

250 300 350 400 450 500 550 600 650 700

Absorbance (AU)

Fig. 9D.9Absorption spectra in the visible region of a catechin-Mv3glc direct condensation dimer
as a function of pH (adapted from Salas et al. 2004b with permission from Elsevier)

could oxidize to the corresponding F-A+pigments, whereas the latter seem to

yield preferentially doubly-linked A-F colorless structures (Bishop and Nagel 1984;

Remy-Tanneau et al. 2003) or rearrange towards yellow xanthylium ions (Jurd and

Somers 1970; Due ̃nas et al. 2006; Liao et al. 1992). Recent evidence has been

obtained regarding the presence in wines of colorless A-F adducts (Remy et al 2000)

and F-A+pigments (Alcalde-Eon et al. 2006, 2007; Salas et al. 2004a, 2005;

Vivar-Quintana et al. 1999). The latter show absorption spectra and color char-

acteristics similar to anthocyanins being subjected to color modifications by the

effect of pH (Fig. 9D.9), and they can also be supposed to be sensible to sulfite
bleaching (Salas et al. 2004b). A hydration constant of 2.64 has been calculated

for the dimer catechin-malvidin 3-glucoside similar to that of malvidin 3-glucoside

(Cheynier et al. 2006). Even if their contribution to the pigment composition in red

wines seems to increase slightly during aging, their levels remain low (Alcalde-

Eon et al. 2006; Boido et al. 2006), which linked to their pH-induced discoloration

lead to suppose that they do not contribute in an important extent to the color of red

wines.

9D.2.3.5 Other Pigments

Other pigment families have been shown to occur in red wine, like anthocyanin

oligomers (Salas et al. 2005; Vidal et al. 2004a), caftaric acid-anthocyanin adducts

(Sarni-Manchado et al. 1997) or catechin-pyrylium derived pigments (i.e., oaklins)

resulting from the reaction between catechin and wood aldehydes, like coniferalde-

hyde or sinapaldehyde (de Freitas et al. 2004; Sousa et al. 2005). These