The Bound Anthocyanins to Protein-Precipitable Tannins ratio (bANT:pTAN) is a useful metric for understanding astringency in red wines. Free Anthocyanins increase the polarity of the Tannins they polymerize with, thus decreasing their astringency. Bound Anthocyanins are also more prone to folding, making them good precursors to colloids which incorporate structural and flavor compounds together in the finished wine. 0.25: The wine likely has very low perceived astringency. This ratio is commonly achieved by restraining tannin relative to anthocyanin extraction. We generally want to maximize bound anthocyanins, but over-restraining tannins can depreciate mouthfeel by limiting structure. Free anthocyanins aren’t the only compounds in wine that modulate tannin astringency, but they are naturally occurring and highly effective. Think of these ratios like archetypes. They are useful for creating generalizations about astringency and wine style but do not encapsulate a wine's complexity or true nature. We have found these ratios to be generally true, but certainly not without exception. For instance, wines with low structure (pTAN) and a ratio of 0.1 tend not to be astringent, and wines with high structure (pTAN) and a ratio of 0.2 tend to be astringent. This is because oxygen also plays a critical role in modulating astringency by increasing tannin polarity and therefore decreasing astringency. The higher the structure, the more Bound Anthocyanin and oxidation are required to incorporate astringency into the mouthfeel. This is why wines from Barolo often need decades to age before consumption, and wines from Napa Valley can be consumed sooner despite often having similar ranges of tannins. Nebbiolo is a low-color varietal and Cabernet Sauvignon is a high-color varietal. To learn more about the bANT:pTAN ratio and how it applies to winemaking, become a Bound advising client.
