9D Influence of Phenolics on Wine Organoleptic Properties 541
could be related to their free concentrationsrather than to their total concentrations.
Therefore, although the anthocyanins themselves may not contribute to taste, they
could somehow modulate astringency and bitterness in wines perception through
the retention of flavanols and other phenolics in the copigmentation complexes, thus
reducing the levels of their free forms. In spite of the knowledge accumulated over
the last few decades there are still manygaps to fill about copigmentation and its
implications on color and other sensory properties of the wines. Among them, it is
necessary to know more about the efficiency as copigments of the different grape
components, which anthocyanins are better candidates to participate in the process,
which are the optimal total and relative concentrations of anthocyanins and cofactors
to provide a suitable color and, in summary, which is the more suitable phenolic
profile of grapes and wine to favor a stronger copigmentation and a good and more
stable color.
9D.2.3 Changes During Wine Maturation and Aging
9D.2.3.1 Nature of the Pigment Material
It is very well known that during wine life a shift in the color of red wines is
produced from the purple-red hue of young red wines to orange-brick hues typ-
ical of the aged ones. This change is explained by the progressive displacement
of grape anthocyanins by more stable pigment structures that are less sensitive to
the pH value and sulfur dioxide bleaching than anthocyanins, thus being able to
express their color in wine conditions at which the anthocyanins are mostly color-
less (Vivar-Quintana et al. 2002). These pigments have been classically designed as
“polymeric pigments” that are associated with the non-dialysable coloring mate-
rial that remains in the aqueous phase after extraction of the red wine by iso-
amyl alcohol (Somers 1971). They were long believed to result from reactions
involving anthocyanins and/or tannins, either director mediated by acetaldehyde
(Haslam 1980; Jurd 1969; Somers 1971; Timberlake and Bridle 1976), and over the
last two decades many of these pigments have been positively identified in wines.
A comprehensive relation can be found in the article of Alcalde-Eon et al. (2006)
where more than one hundred derived pigments detected in red wine are listed.
However, all of the identified pigments are rather relatively small molecules, thus
raising doubts about the actual polymeric nature of the wine pigments.
A method for the fractionation by column chromatography of the coloring mate-
rial of red wines in three fractions corresponding to anthocyanin monomers, and the
so-called “red polymers” and “brown polymers” was proposed by Bourzeix et al.
(1980), who roughly estimated the molecular weight of the red polymers in 560,
meaning that they would not consist of more than two flavonoid units. No indica-
tion about the size or nature of the brown polymers was made. It is usually assumed
that polymeric pigments are responsible for the “humps” observed in the RP-HPLC
chromatograms obtained for matured and aged red wines. Fractionation of red wines
to separate and collect the hump material in order to characterize it further has
been tried by some authors (Mateus et al. 2002a; Remy et al 2000; Salas et al. 2005;