Grapes develop sugar as they ripen. They do not become sweeter once picked. This is why harvest timing is critical. Picking grapes is the single most important decision that the winemaker must make. Once they are picked, you cannot go reverse it. You are committed.
Each variety of grapes has a window of time when it has reached maturity. Moreover, different grapes mature at different times. Picking the grapes when they reach optimum ripeness has a direct bearing on wine quality and its ability to satisfying the specific wine's flavor goal. This is one of the hardest tasks a winemaker has, as Mother Nature does not always keep to a schedule.
Ripeness is in the eye of the winemaker. They commonly have a target for grape ripeness goal for the each wine they will produce. Again, that target can vary depending on the style of wine to be made. For example, a Pinot Noir production for sparkling wine will have a very different ripeness target compared to that for a Pinot Noir for a still wine. There will never be a single set of guidelines defining ripeness for a grape variety under all circumstances and purposes.
For consistency in wines, many winemakers will measure the sugar, acid, and pH of the grape. Winemakers will base their decision when to harvest the grapes on their experience and knowledge of each vineyard. They also take into account the weather forecast for the forthcoming weeks. Finally, they will constantly evaluate the color and taste of the grapes and will sample them regularly, starting around the beginning of September.
Contributor: WineDefintions Staff Writer