474 N. Terrier et al.
Lee 2002). The amount of flavonols ranged between 2 and 30mg/kg of berry for
white skinned cultivars and 4 and 78mg/kg of berry for black skinned cultivars
(Mattivi et al. 2006). Rodriguez Montealegre et al. (2006) agreed that red skinned
cultivars contain more flavonols but they detected higher concentrations, up to
170mg/kg for Viognier berries or 200mg/kg for Shiraz berries.
Flavonol and especially quercetin levels in the skins of Pinot noir grapes showed
a dramatic response to sun exposure (Price et al. 1995). The effect of bunch shading
on flavonol accumulation was confirmed in Merlot (Spayd et al. 2002) and Syrah
(Downey et al. 2004) while temperature had little or no effect. This suggests that
biosynthesis of flavonols islight-induced, accordingly with the role of flavonols as
UV-protectant (Cortell and Kennedy 2006; Downey et al. 2004; Spayd et al. 2002).
This effect was maximum when shading was applied a few weeks before flower-
ing, almost preventing any flavonol synthesis. When the treatment was applied after
flowering, the amount of berry flavonols was 8–10 times lower than in the control
berries (Cortell and Kennedy 2006; Downey et al. 2004). No detailed impact on
the different grape flavonols in skins is available. The flavonol content in pulp also
discriminated between shaded and light exposed berries, kaempferol and quercetin
derivatives being more abundant in the pulp of sun exposed berries, and myricetin
derivatives, along with other unidentified flavonols, in that of shaded berries (Pereira
et al. 2006).
9B.2 Extraction into the Wine
Wine flavonoid composition depends not only on the grape composition but also on
their extraction and subsequent reactions during the wine-making and aging process.
Thus, white wines obtained by direct pressing with minimum skin contact contain
mostly the flavonoids originating from pulp. In ros ́e and red wine technology, the
procedures used to extract the anthocyanin pigments from the skins also result in
increased extraction of other flavonoids from skins, seeds and eventually stems or
leaves if present in the fermentation tank. Extraction continues until the wine is
separated from the solid residue (marc or pomace) by racking or pressing. Its kinet-
ics depend on the solubility of the compounds and on their accessibility within the
berry tissues, which can be modulated by physiological factors such as the mat-
uration stage. It is further influenced by other technological factors, including the
concentration of alcohol and of sulfur dioxide in the liquid phase, the temperature
and the extent of must homogenization. Consequently, the wine flavonoid composi-
tion is influenced by the duration of pre- and post-fermentation maceration phases
and by treatments enhancing cell wall or berry degradation (e.g. use of pectinolytic
enzymes).
9B.2.1 White Wines
Quercetin 3-glucuronide was the only flavonol detected in free run juices and wines
(Alonso et al. 1986; Betes-Saura et al. 1996), along with trace amounts of kampferol