Verjus is the pressed, unfermented juice of unripe wine grapes. It was first used in the sixteenth century, probably “as a result of the right given to peasants to pick the unripe grapes from the second growth left on the vine by vineyard owners,” says historian Carolyn Smith-Kizer.

It can be used as a meat tenderizer, a cocktail base, and even as an indigestion cure, but its greatest advantage is in food and sauces. It’s great in vinaigrettes, in rich sauces, and as a chicken or red-meat marinade. With its delicate sweet-sour balance and low acidity, it doesn’t fight wine served with the meal as vinegar often will.

Karin Warnelius and Justin Miller of Terra Sonoma in Northern California’s Alexander Valley are some of the few domestic producers of verjus. They wanted to do something with their unripe fruit besides composting it. “We’re very into using all of the land and not wasting anything,” says Warnelius. “For us to start making verjus was a natural step.”

A 375ml bottle of verjus is $15 at www.terrasonoma.com.