How do I know when to harvest grapes?
Grapes must be harvested at the right stage of maturity to ensure high quality. There are several indicators of grape maturity. Color, size, sweetness, and flavor of the berry are the most useful indicators. Depending upon the variety, berry color changes from green to blue, red, or white as the grapes approach maturity. Color alone, however, should not be the sole basis for harvesting grapes. Berries of many varieties change color long before they are fully ripe. At maturity, individual berries are full size and slightly less firm to the touch. As a final test, taste a few grapes for sweetness when berry size and color indicate the fruit is approaching maturity. Harvest grape clusters when berries are sweet. Grapes will not get any sweeter after harvest.
When harvesting grapes, remove clusters with a knife or hand shears. Sound grapes can be stored in perforated plastic bags in the refrigerator for up to two months. Grape harvest requirements for wine making are much more precise than those for fresh consumption. White grapes are harvested when berry pH reaches between 3.1 and 3.3, and red grapes are harvested at a pH between 3.3 and 3.4. The titrateable acidity should be 7-9 g/l. Maximum sugar levels are highly desirable.