9D Influence of Phenolics on Wine Organoleptic Properties 545
de Freitas (2001) when measured at their maximum wavelengths in methanol/HCl
0.01%. Nevertheless, at wine pH conditions the difference between the extinction of
both pigments must be higher in favor of the pyranoanthocyanins, due to its greater
resistance to pH bleaching. This was clearly shown by Hakansson et al. (2003),
who found that at pH 1.5 the vinylsyringol and vinylcatechol adducts of malvidin
3-glucoside (pinotin A) possessed about one-third of the molar extinction coefficient
of the anthocyanin (27,600). However, in model wine (pH 3.6) closer extinctions
existed for the three pigments (7,100, 10,000 and 6,200 for malvidin 3-glucoside
and its vinylcatechol and vinylsyringol adducts at their maximum wavelengths in
the visible region, respectively). This suggests that, for a same concentration and
at wine pH, the color expression of these pigments would be rather similar and,
thus, in wine their contribution to the color would mostly be depending on their
concentrations (Rentzsch et al. 2007). However, Schwarz and coworkers found the
visual detection limits for malvidin 3-glucoside, pinotin A (Schwarz and Winter-
halter 2004) and vitisin A (Schwarz et al. 2003) at wine pH to be 0.14, 0.03, and
0.07 mg/mL, respectively, pointing out that for the same concentration pyranoan-
thocyanins would show higher color expression than anthocyanins.
Estimations about the actual contribution of pyranoanthocyanins to the color of
red wines differ according to the authors, which may be due to the types of wines
studied and the way used for pigment calculation. Alcalde-Eon et al. (2006) found
that 70% of the pigments in a two-year old red wine were still anthocyanins, and
that pyranoanthocyanins represented about 15%. If one assumes the observations
of Schwarz et al. (2003) that pyranoanthocyanins have a visual impact 2–4 times
greater than anthocyanins, and taking into account that the percentage of antho-
cyanins expected to be in colored forms at wine pH would be around 15% (Brouil-
lard 1982), this would mean that a relevant part of the color of those wines would
be determined by the pyranoanthocyanins. There is nothing to say in older wines in
which the pyranoanthocyanins could be the most abundant pigments representing up
to 50% of total pigments, as determined by Boido et al. (2006) in a 64-months-old
wine sample. Monagas et al. (2006) using chromatic and polynomial regression
analyses to evaluate the influence of the different pigment families in the color
of red wines up to 26 months of bottling concluded that both anthocyanins and
pyranoanthocyanins were involved in the definition of the color. Among these, the
pyruvic acid adducts (i.e., carboxypyranoanthocyanins) were those that provided
the best model for predicting most of thecolor parameters. These views do not
seem to be shared by Schwarz et al. (2003) that estimated that the contribution of
carboxypyranoanthocyanins (vitisins A) to the color in aged red wines would be
below 5%. This sounds logical since the formation of those pigments in the wine
takes place in early stages to further decline (Alcalde-Eon et al. 2006).
A particular type of pyranoanthocyanins derivatives are the vinylpyranoantho-
cyanin-flavanol pigments, first described by Mateus et al. (2003) and also called
Portisins (Mateus et al 2004b), which were isolated from Port wines. These pig-
ments have particular chromatic features. Their absorption spectrum in the visible
region is largely shifted towards higher wavelengths (Fig. 9D.7) and they show a
blue color, likely due to the extended conjugation of theirπelectrons, which confers