SP307-N-Selecting Quality Grapes

The grape is a very versatile fruit. The wide array of uses for it include fresh consumption (table grapes), raisins, jellies, jams, pies, juices, wines or blends with other fruits in numerous products. The degree of fruit ripeness needed will vary somewhat, depending on the intended use of the grapes. Therefore, an awareness of the ripening process and its impact on fruit quality is important for consumers as well as home and commercial grape growers. Grapes undergo many changes during the ripening process. As this process proceeds, it may be difficult to select the time at which the grape is ready for harvest.

Veraison is the start of the ripening period. It is physiologically related to coloration. White grapes will change from green to yellow or white. Red grapes change from green to light red and finally to dark red. Blue-black varieties will change from green to red to blue and finally to blue-black. At the same time, berries will begin to swell and become elastic. Sugar levels within the fruit will begin to increase rapidly.

A period of maturation stretches from veraison to the final stage of maturity. This stage may last upwards of 40 to 50 days. During this time, the grape will continue to swell, gather sugars and lose acidity.

Physiological maturity of grapes is defined as the stage when the fruit reaches its largest diameter and maximum sugar content. Technological maturity defines the picking time in relation to the ultimate utilization of the grape. The dates of physiological and technological maturity do not always coincide. In this fact sheet, the term maturity will refer to technological maturity.