Napa Valley Cabernet Sauvignon Proanthocyanidin Changes During Fruit Ripening: A Multi-Appellation Survey

Area of Science:

• Viticulture
• Enology
• Plant Biochemistry

Background:

• Flavonoids, particularly proanthocyanidins (PAs), significantly impact wine mouthfeel attributes like astringency.
• Understanding PA variability is crucial for predicting and controlling wine sensory characteristics.

Purpose of the Study:

• To investigate the distribution and variance of winegrape flavonoids during ripening in Napa Valley Cabernet Sauvignon.
• To identify key parameters controlling proanthocyanidin (PA) activity and astringency.

Main Methods:

• Whole berry partial extractions were performed on Cabernet Sauvignon grapes throughout the ripening phase.
• Multivariate analysis was employed to assess the relationship between PA characteristics and ripening stage.

Main Results:

• Seed PA material was the primary driver of PA activity early in the ripening phase.
• Pigmented polymer formation later in the season led to a decrease in PA activity.
• Molecular mass and pigmentation of PAs were identified as the main drivers of changes during ripening.

Conclusions:

• Significant variability in PA activity exists even within small geographical areas like Napa Valley.
• These findings suggest potential for vineyard manipulation to influence PA activity and wine mouthfeel.
• Further research is warranted to target specific variables affecting PA activity for controlled winemaking outcomes.