Verjus is a tart, fresh juice of unripe wine grapes. Verjus or Verjuice as it is sometimes called, literally means green juice in the sense that it's made from fruit that has yet to fully ripen — it's green.
This Napa Valley Verjus is made from wine grapes removed from the vine in midsummer, at a point in the growing cycle called veraison. At veraison, red wine varieties such as Cabernet Sauvignon and Merlot change in color from green to black and the berries begin to soften enough to press.
It is used to add acidity to foods, an important component in food and in cooking. It is a culinary ingredient indigenous to the world's wine producing regions that is used in sauce making, for poaching fish and meat, and to dress lettuces, vegetables and fruit.