Tannins continued oxidation

During aging the anthocyanins continue to disappear by condensing with tannins which themselves undergo an oxidative condensation resulting in a color shift from yellow to orange-brown. Finally it is these tannins which play the most important role in the characteristic color of old wines. 

Continuous operation possible high output few breakdowns high tannin and suspended solids content severe oxidation... 

Amplification of the oxidation-reduction potential is not the only cause for diversity of secondary metabolites in angiosperms. In order to understand the phenomenon more fully it is necessary to remember also the best known of the evolutionary trends the gradual substitution of woody forms by herbaceous ones that operate in several lineages. Reduced utilization for the production of lignins and condensed tannins should cause initially a surplus of cinnamate, raw material for the biosynthesis of allelochemicals of primitive angiosperms. The continuing decrease in the importance of the shikimate pathway and the connection between primary, and secondary metabolism requires that the transition from the woody to the herbaceous habit be accompanied in the long run by a curtailment of shikimate precursors for the biosynthesis of allelochemicals. Let us look now into the evidence for these postulates. 

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