A unique and multi-purpose alternative to vinegar, verjuice - or verjus - is a delectable, sweet-tart liquid extracted from unripened green grapes. A favorite among cooks in the Middle Ages, this clear juice is less acidic than lemon juice like wine and will never interfere with the inherent flavors of wine. Use verjuice to bring out the best in soups and sauces, as a marinade, or for deglazing. Store in the fridge once opened.