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

Micro-oxygenation in Contemporary Winemaking7.4 KEY FINDINGS OF IDENTIFIED STUDIESThe key findings of the 19 identified scientific studies on micro-oxygenation aresummarised in Table 19. The table shows the significant changes in MOX treated winesrelative to control wines, though the timing of the measurements may differ betweenstudies.7.4.1 Impact on ColourThere are now a number of studies which clearly demonstrate that micro-oxygenation hasbeneficial effects on wine colour. Colour intensity is significantly increased (or decreasedless than controls) by MOX, and treated wines are more resistant to SO 2 bleaching thancontrol wines. These results are consistent with the predicted oxidative reactions discussedin 6.2.2. Micro-oxygenation does appear to result in the production of larger polymericpigments which preserve wine colour.Although the postulated formation of pyranoanthocyanins should cause a shift towardsorange, the empirical results reveal no clear pattern with regard to changes in wine hue.7.4.2 Impact on Phenolic CompositionChanges in phenolic composition after micro-oxygenation have also been well studied.Earlier studies found a decrease in the total phenol concentration relative to controls butmore recent research has shown no significant differences between treated and untreatedwines (Table 19).One of the most constant patterns in the literature reviewed here is that MOX treatmentproduces an increase in measured polymeric pigment compounds while free anthocyaninsand tannin monomers are decreased. Again this is consistent with the theoreticaloxygenation reactions and the observed colour changes.However, the increase in pyranoanthocyanins that should occur with micro-oxygenationhas not been clearly proven. del Carmen-Laudy et al (2006) and Pérez-Magariño et al(2007) found no difference relative to controls although two recent studies foundsignificantly higher levels of pyranoanthocyanins in treated wines (de Beer et al., 2008;Cano-López et al., 2008). Cano-Lopez (2006) showed an increase in pyranoanthocyaninsimmediately after micro-oxygenation but a higher rate of breakdown of these compounds in63