Grape growth and wine production are dependent on location, temperature, and time. The time required for grapes to ripen also varies by species of grape and location of the grape cluster on the vine. There are two main regions on a grape vine, the fruit region (FR), and outside the fruit region (OFR). The FR is the lower-middle area of the vine where the majority of the fruit grows. The region OFR consists of the upper part of the vine where there is less fruit and more foliage. Throughout many harvest periods, Fero Vineyards & Winery has determined that grapes in the OFR ripen at a slower rate than the fruit in the FR. This is due to the amount of direct sunlight and leaf exposure. FR grapes receive a moderate to high amount of direct sunlight because the leaves are pruned in this area and are not covering the fruit. The OFR grapes receive less direct sunlight because they are covered by leaves. Direct sunlight has photosynthetic effects on ripening rates of grapes through its effects on the vine’s leaves. This is because leaves provide the grapes with sugar to make them sweeter. Thus grapes outside of the fruit region do not receive the benefits of sunlight which affects their rate of ripening. Wine production proceeds almost exclusively from FR grapes, presenting an opportunity to reduce waste and increase production by determining when OFR grapes can be harvested.
While general characteristics of wine grape behavior is well known, regional variations in climate and sunlight require any model of grape ripening to be based primarily on local data. This research project focuses on the time dependence of ripeness for Pinot Noir, Lemberger, Riesling, and Gruner Veltliner grapes both FR and OFR. Ripeness is determined by the balance of brix (sugar content), ph, and titratable acidity. This data will aid Fero Vineyards & Winery in harvest time estimates and possible economic benefits from creating new OFR-based products.
Sources:
Zoecklein, B W, and B H Gump. Evaluation of Grape Maturity and the Factors Impacting Maturity. www.apps.fst.vt.edu/extension/enology/downloads/wm_issues/Fruit%20Maturity/Evaluation%20of%20Grape%20Maturity%20and%20the%20Factors%20Impacting%20Maturity.pdf.
