According to GrapesWeb.com, archeological evidence suggests that wild grapes were made into wine long before grape vines were domesticated. There are now over 5,000 varieties of grapes grown on every continent of the world for wine. The flavor of wine is greatly affected by the time in which grapes are harvested.
Grape cultivation for wine began approximately 6,000 B.C. In ancient Egypt, red grapes were grown along the Nile to make red wine. The ancient Romans first developed practices that are still in use today to make wines. Over 90 species of grapes were grown in the Roman Empire on large plantations to make wine. The early Romans harvested grapes based on the color of the grape skin, taste of the grape, and the look of the seeds.
According to Mother Earth News, wine grapes must not only be picked when ripe, but also when they are mature. Grapes that have been picked must immediately be brought to the wine press and crushed for their juice. Mature grapes have an optimal level of sugar in them. This creates the perfect balance of alcohol, tannin and flavor. If a grape is left on the vine too long, the wine will contain too much alcohol when it is made and the flavor of the alcohol will overwhelm the flavor of the wine.
When determining the proper time to harvest grapes, you can examine an individual grape in a cluster for clues that will point to whether the grapes are ready for harvest. Grape size is one determining feature. Small grapes contain little juice and thicker skin, but the skin is flavorful and the grape juice will be concentrated and flavorful. Large grapes will have a thinner skin and more juice. Smaller grapes are ideal for wines.
The ancient Romans relied on the taste of grapes to determine their maturity. Modern grape growers can scientifically test grapes for maturity using a hydrometer. A hydrometer examines the specific gravity of liquids. You can pick up a hydrometer at a winemaking supply shop. A hydrometer will help measure the sugar quantity of the grapes. Winemaking grapes are mature when they reach a specific gravity of 1.105.
Another sign that can help you determine if grapes are ripe is to examine the seeds. Seeds that are green are a sign that grapes are not mature yet. Seeds that are mostly dark or brownish are a sign of a ripe, mature grape that is ready to harvest.