Verjus is the name given to the juice taken from unripened white grapes. At the time, there were three different sorts of grapes: one for wine, one for the table, and one for verjus. Verjus is acidic and was thus used as an alternative to lemon juice. In 19th century, a change in tastes meant that acidity was considered common and vulgar. As a result, the verjus, whose taste was particularly strong, was gradually replaced by citrus fruits, initially orange, then lemon.
The fresh grapes would be peeled and depipped. They were then pressed into a syrup, into crystalised verjus or indeed verjus conserves, the latter of which were greatly sought after and very expensive due to the need for just as much sugar as verjus to make them. The juice was kept in bottles and used as a base for sauces, serving as an alternative to vinegar.
It was said that a small glass of verjus was an excellent “pick-me-up” after a fall.