The grape harvest in California is just around the corner. With the huge amount of sunshine we’ve received this summer, there should be no problem in ripening the fruit. Most of us would think ripe means sweet….after all, how many times have we heard a winemaker discuss picking grapes at a certain level of “Brix?” (Brix is a test that measures sugar content.) This indicator, however, is not the only indicator of what makes a great wine. As scientists have refined their understanding of the ripening process, winemakers are now steering away from using a single index of grape maturity.
Without going too science-nerd on you, let’s review what happens to grapes during their final stages of ripening. The most noticeable changes occur in their exterior skin colors. Called “verasion” (when a red wine grape, such as Cabernet, changes from green to red and then to black) color pigments are deposited in the grape’s skin. Verasion also occurs in white wine grapes when colors change from green to yellow and then to deep golden. These are just the tip of the iceberg to the unseen chemical transformations occurring inside the grapes.
The interior of the fruit is busy accumulating sugar. At the same time of increasing sweetness, another important process is occurring: acid levels are dropping. But, these are just two of the many complex physiological alterations inside the grape. Tannins also are changing, becoming less aggressive and bitter-tasting. Other biological are underway making the grape taste less herbaceous. All of these changes are highly significant to the winemaker.
Today’s winemakers view ripening as two completely different processes. Sugar ripeness refers to the breakdown of acids and simultaneous accumulation of sugar. Flavor ripeness (physiological ripeness) encompasses all the other complex chemical changes, such as tannins softening, skin pigments darkening. In a perfect winemaking world, both of these processes would occur simultaneously. They do not.
Sugar and acid balance are instrumental in making wine, but they are not the perfect indicator of a great wine. Sugar and acid balance cannot predict the ripeness of flavors or aromas. In spite of a plethora of modern technology, there is no single index for determining flavor ripeness. In fact, the best determinant for verifying physiological ripeness is very low tech---taste. In concert, the winemaker must rely on experience and instinct as most of the fruit flavors aren’t released until fermentation.
Next time you’re having a glass of vino, focus on the aromas, flavors and mouth-feel. These come from flavor ripeness.