VERAISON

Veraison begins with coloration and ends with the complete transition from green to black berries. As a baseline, we begin berry measurement at the start veraison to track color development in the skins. Interestingly, the start of veraison also coincides with peak tannin concentration which will progressively decrease as oxidation lignifies the seed coat (Kennedy et al., 2000). Tannins will decrease in activity and become less extractable, but we almost always consider them abundant. We continue measuring grapes weekly through ripening until harvest. Monitoring berry anthocyanin accumulation weekly is fundamental for understanding how a vineyard responds to varying environmental conditions and practices. Between the start of veraison and the end of ripening is a window of time for grapes to accumulate anthocyanins and other metabolites. While veraison is a critical time for quality development, grapes are also protected by the momentum of their growth. Firm berries protect the grapes from dehydration and an active vine metabolism promotes recovery after stressful events. Particularly in the case of anthocyanins, environmental stress like heat waves stunts their peak potential for that vintage. 

References

Kennedy, J. A., Matthews, M. A., & Waterhouse, A. L. (2000). Changes in grape seed polyphenols during fruit ripening. Phytochemistry, 55(1), 77–85. https://doi.org/10.1016/S0031-9422(00)00196-5