When The Grapes Begin Their Surge To Ripeness
Verasion is the term used to describe the changing colors of grapes as they ripen. Grape clusters start out green, and as they ripen, the red varieties start turning red, and the white varieties start turning golden or slightly pink, brown or gray. It also signals a shift in the development of the grape from rapid growth to the long process of ripening. Click play below to view a video of verasion.
At the beginning of verasion, the berries are hard, green and about the size they will be when fully mature. In addition to the outward changes to the berries, this period marks an increase in the level of brix, or fermentable sugar produced in the grapes, and a decrease in the level of acidity. At this point, the sugar level is about 5%. Starting soon, the grapes will begin to accumulate sugar at a rapid rate and lose acidity on an equal level. Over the next couple of months, the sugar level will steadily increase until it approaches 25 brix, which is about the sugar level we want at harvest time. At the same time, the acid level (expressed as Tartaric acid) will decrease from about 30 grams per liter to around 5.5 grams per liter.
During this rapid growth phase, the grapes need warm days with temperatures between 80 and 90 degrees and no rain. Nighttime temperatures will be in the 50’s and 60’s. And our irrigation regimen must be judiciously applied at a minimum level to prevent the vines from becoming overstressed.
During verasion the grape bunches do not ripen uniformly. This means that some portion of the bunches may have significant quantities of green grapes while the rest of the bunches are purple. As a quality requirement we will be closely monitoring the bunches and will remove (green harvest) the bunches that are not at least 80% purple. If this were not done, the crop at harvest would not have uniform maturity levels. Thinning will insure a more uniform maturity at harvest resulting in a higher quality wine.
A lot is known about verasion but what triggers the process remains a mystery. Perhaps there is still mystery and mystique in bringing wine to the table?