This is a topical issue at the moment as thousands of pickers are preparing to harvest the next vintage. Above all, OPTIMAL maturity is a purely theoretical value, because it mostly depends on the style of wine that we want to create. Beyond that, OPTIMAL maturity is indeed linked to factors such as grape variety, climate, terroir and weather conditions, and last but not least to the skill and chance of a winemaker or vintner.
Different components of the grape may be of interest for the winemaker at harvesting time. There are obviously the sugars and acids, but alsoethe primary aromas, anthocyanins (the red colour of grapes) and optionally the tannins. All of them molecules we might want to rediscover in our wine. They all start ripening from veraison on, but not necessarily at the same speed. The sugars increase, acidity decreases, the amount of flavors is growing and diversifying, tannins are increasing in the skin and seeds and become more palatable. But a large amount of sugars frequently is achieved early, while the tannins need more time for ripeness. Depending on the desired wine, winegrowers and winemakers at a certain point have to take decisions and choose tastefull and balanced grapes, according to the wine they want to make. Because OPTIMAL maturity is, above all, a matter of taste and balance!
An example ? GRENACHE NOIR allows both to develop great wines for aging, as well as pleasant and very drinkable rosé wines. In the first case, the winemaker will primarily be interestd in the maturity of the tannic structure. In the case of rosé, fresh flavors and a balance between sugars (which will become alcohol) and acids will be critical. Grapes intended to be used for rosé making will therefore certainly be picked earlier than grapes for making a fullbodied red GIGONDAS or MINERVOIS wine.
In summary: According to ripeness, each variety allows to develop different styles of wine. As the soil, the climate and the vintage have a more or less strong influence on the ripening of grapes, it’s up to winemakers to choose the OPTIMAL maturity, and set the ideal harvest date for their “dream wine”.