Grape berries start out with a low pH and a lot of natural acids in their juice. As the berries ripen, they lose acid, and their pH rises. Natural acidity is critical to producing balanced and long-aging wines, so we watch this transformation carefully as the grapes ripen. Picking too early, regardless of brix, can produce wines with too much acid, while picking too late can produce wines that taste “flabby” due to a lack of natural acidity to support and to lift the palate.

Compounds called phenols influence the final color, the mouthfeel and texture, and the taste of wines in big, big ways. For instance, tannins are phenols. These compounds are produced in the skins, the stems, and the pips of the grapes, and they take lots of sunlight, heat, and time to develop fully. There is no reliable measurement scale, like brix or pH, to monitor the phenolic ripeness of a grape. (Phenolic ripeness is also referred to as physiological ripeness). Instead, a winemaker has to taste the grapes and has to be able to know when they are finally a peak ripeness. This is probably the single most important and most influential decision that a winemaker makes during the entire winemaking process. Some of the most interesting, ethereal, long-lasting, and unique pieces of a wine’s final flavor are a result of these phenolic compounds. Pick too early, and they taste harsh and “green.” But pick too late, and they change and even disappear altogether.