The grapes are following suit with all of the other fruit crops at the Missouri State Fruit Experiment Station – they are ripening early this year. The grapes are about two weeks ahead of schedule at this point. The sign that grape ripening has begun is veraison. Veraison is the stage when the grape berries soften and the colored grapes start to change from green to red or purple and the “white” grapes change from an opaque green to a more translucent green or golden color.
Mars purple/blue seedless table grape has begun veraison this last week of June. Mars is a cultivar release from the University of Arkansas breeding program. It is similar to Concord except that it ripens earlier and is seedless. It is often ready to pick in early August in southern Missouri at Mountain Grove. It is resistant to disease and to bird depredation. In southern Missouri, Concord does not color as well as in cooler areas. Sunbelt is another release from the University of Arkansas breeding program that is similar to Concord, but ripens more evenly in our area. Sunbelt has large blue/purple berries in small clusters that are ready for harvest in mid-season. Mars, Concord and Sunbelt are winter cold hardy, bird-proof cultivar choices for the home gardener who wants to produce grapes for fresh eating, juice or jelly. Concord and Sunbelt are also suitable for home winemaking.
Mars is not typically used as a wine grape, so we just taste test it to see if it is ripe enough to harvest. Harvesting the grapes used for wine is quite a different story. Once the color has changed and the berries have sized, grape berry samples are collected at intervals and the sugar, pH and acid levels are determined. Closer to harvest, a process to assess the sensory characteristics of the berry by tasting the seeds, pulp and skin separately is employed. Why all this bother? It is because grapes will not ripen further after harvest, so you need to pick them at their peak.
White wine grapes are harvested when berry pH reaches between 3.1 and 3.3, and red wine grapes are harvested at a pH between 3.3 and 3.4. The pH in these specific ranges is important so the wine does not spoil. The titratable acidity is also measured and should be 7-9 g/l in table wines. Sugar levels are also measured. The balance of sugar and acid is important in wine. If the wine doesn’t have enough acid, it tastes flat, but if it does not have enough sugar, it tastes too sour.
If you are interested in home winemaking, be sure to visit our home winemaking display at the Missouri State Department of Agriculture booth at the Ozark Empire Fair from July 27 through Aug. 4. If you are interested in making wine this year, check out our online publication “Making Wine for Home Use” at http://mtngrv.missouristate.edu/assets/publications/MS28MWFHUweb.pdf
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