By Harold McGee
Grapes are the berries of woody vines in the genus Vitis. V. vinifera, the major source of wine and table grapes, is native to Eurasia. There are also about 10 grape species native to temperate Asia, and 25 to North America, including the V. labrusca that gives us Concord and Catawba grapes. About two-thirds of the world’s grape production goes to make wine; of the rest, about two-thirds are eaten fresh and a third are made into raisins. There are many thousands of grape varieties. Most wine varieties originated in Europe, while varieties for eating fresh or making into raisins can often be traced back to western Asian parents. Wine grapes come in relatively small clusters and are acidic enough to help control the yeast fermentation; table grapes come in large clusters and are less tart; raisin varieties have a thin skin, high sugar content, and loose cluster structure to facilitate drying. The commonest table and raisin grape in the United States, the Thompson seedless or sultana, is a variant of an ancient Middle Eastern all-purpose variety, the Kishmish.