micro-oxygenation in contemporary winemaking - Cape Wine ...

Micro-oxygenation in Contemporary Winemakingphenolic acids act as precursors for the formation of the volatile phenols, a wine faultassociated with Brettanomyces spoilage. However, the main role of the phenolic acids is tocontribute to the anti-oxidant capacity of both red and white wines. For example the tartaricesters of hydroxycinammic acids (particularly caftaric acid) are centrally involved inoxidation and browning reactions in white wine (Ribéreau-Gayon et al., 2006c).The other important group of non-flavonoid phenols are the stilbenes (Table 11). Thesephenols have attracted significant attention in recent years because compounds such astrans-resveratrol are thought to be responsible for many of the beneficial health effects ofred wines (Corder et al., 2006).6.1.3.2 Flavonoid PhenolsMore important in terms of the subject of this report are the flavonoid phenolic compounds.They are responsible for the red pigments, yellow pigments and tannins of grapes andwine. Flavonoids are mostly derived from the skins and seeds of grapes. They share abasic 15 carbon structure (Figure 7) which consists of two phenolic rings (Ring A and RingB) connected by a short three-carbon chain, though the three carbon chain is frequentlyclosed by oxygen to form an oxygen heterocycle (Ring C) (Heim et al., 2002).A423BAOCBBasic flavonoid structureFlavonoid with oxygen heterocycleFigure 7: Flavonoid Ring StructureThe flavonoid phenols are organised into a number of different groupings, though thenames for the different categories is certainly confusing for the non-expert. The maingroups in wine and some of the important members of each group are presented in Table12. The groups are distinguished by differences in the central ring structure (Ring C) andby substitutions on the B ring. The most important flavonoids in grapes and wine are theanthocyanins, the flavanols, and the flavonols 1 .1Notice the subtle difference in nomenclature between flavanols and flavonols.38