Verjus?

Yup- Verjus. Green Juice. The juice of unripe grapes: bright, non-alcoholic, not as acidic as vinegar;  low in sugar; fresh and fruity; and a "secret ingredient" that makes otherwise "difficult-to-pair-with wine"  food more wine friendly.

It's a classic alternative to vinegar

 used in marinades, salad dressings, pan sauces, and mustards; and comes in red (from red or a combination of red and white grapes, either fruity and soft, or bigger  with earthy notes), and white (pictured here), which tends to be  lighter and crisper.

Here in Oregon, Abacela Winery in the Umpqua Valley, and Montinore Vineyards in the Willamette Valley produce beautiful versions from fruit that is "green harvested", pruned while still unripe to decrease overall yield and improve ripening, sugar levels, and fruit concentration of the remaining clusters.  If not made into Verjus, the green harvested fruit is dropped and left in the vineyard as compost.

Here are some recipes to try:

Mix one part of Verjus with 2 parts of sparkling water for a refreshing spritzer.                                            

Try it in place of vinegar in a salad dressing, with 3 parts verjus to 1 part oil.  Salads with vinaigrette are notoriously hard to pair with wine. Verjus is  tart, but produces a softer but still flavorful dressing that pairs well with a fruity white wine. It works with wine because the acids in verjus are grape acids rather than the more pungent acetic acid found in vinegars.

The next time you poach chicken or salmon, try replacing some of the poaching liquid with verjus for a nice kick of flavor. Chicken breast poached this way makes a particularly delicious chicken salad.

Verjus can  be used in place of wine to deglaze a pan, or in place of of vinegar or lemon juice in sauces.

Try it in a Buerre Blanc.

You will need:
1 tablespoon finely chopped shallot
1 cup dry white wine
1/2 cup verjus
1 pound cold unsalted butter, quartered and and cut into 1/2" pieces
kosher salt to taste

Combine the  chopped shallot, wine and verjus in a non-reactive saucepan. Bring to a boil, reduce the heat, and simmer until about 2 tablespoons remain.
Reduce the heat to low, and add the butter 2 pieces at a time, wisking as the butter melts and the sauce emulsifies. When you are ready to add the last two pieces of butter, take the pan off of the heat, wisk in the last of the butter, season to taste with salt, and serve immediatly over fish or seafood.  Makes about 2 cups of sauce.
And as Julia would say, "Bon Appetit".