9D Influence of Phenolics on Wine Organoleptic Properties 533
This latter methodology has hardly been used to evaluate the strength of the
copigmentation effect, although it has been employed to characterise the color of
red wines.
By using Boulton’s method diverse authors (e.g., Darias-Martin et al. 2007; Her-
mosin, 2003; Levengood and Boulton 2004; Schwarz et al. 2005 ) have concluded
that copigmentation could account for up to half of the observed color of young
red wines, depending on the levels of colorless phenolic compounds or cofactors
present, which could even have more importance than anthocyanins to define the
color in those wines.
During wine life a decrease is produced in the concentrations of both antho-
cyanins and cofactors in the wines, so that the extension of the copigmentation
also decreases up to having no influence on the color of aged wines. The results
obtained about the contribution of the copigmentation to the color of red wines
differ among studies. Hermosin et al. (2005), in assays with Spanish wines of the
varieties Cencibel (synTempranillo), Cabernet Sauvignon and Syrah, found that
copigmentation accounted for 32–45% of the color of red wines recently elabo-
rated to decrease to 20–34% after three months and be practically negligible after
nine months (0–5%). In studies carried out with wines made with grape varieties
of the Canary Islands (Listan Negro and Negramoll), Darias-Martin et al. (2007)
calculated that copigmentation contributed 22% and 19% of color in red wines of
one and two years of age, respectively. Similar results were obtained by Lorenzo
et al. (2005) that estimated that around 18% of copigmentation still existed in
their wines after nine months of oak aging. The differences in the results among
authors might be explained by the variations in wine composition, as determined
by grape characteristics and the winemaking processes, which provoke differences
in the type and levels of anthocyanins and cofactors that affect the extension and
stability of the copigmentation process. Further, the conditions of storage and aging,
as well as the scale of the vinifications should also play a determinant role on the
results obtained.
The influence of the ethanol on the copigmentation was studied by Hermosin
(2003). In assays with de-alcoholised wines further reconstituted found that as
ethanol content increased the percentage of copigmentation diminished following
a quadratic relation; with ethanol contents between 12% and 14% the wines main-
tained about three quarters of the copigmentation observed at 0% ethanol. This
observation confirms the dissociating role of ethanol on copigmentation complexes
but also shows that copigmentation still occurs in red wines. In model solutions,
the increase in ethanol in the medium has been seen to induce a bathochromic shift
in maximum wavelength in the visible region of the spectrum in relation to water
(Brouillard et al. 1991). However, this effect was hardly observed in the reconsti-
tuted wines, when only a slight bathochromic shift was observed in wines with
ethanol content higher than 20–22% (Hermosin 2003), suggesting that only some
contribution of this effect to the blue hues of red wines containing higher ethanol
levels (e.g., fortified red wines) could be expected.
Copigmentation may not only affect color definition of red wines but also influ-
ence its stability. Chemical reactions that take place in wines, like oxidation and