"Grape or wine must is the juice pressed from grapes before it has fermented; new wine. Grape must is also used in making traditional balsamic vinegar, which must mature by a long and slow process thought natural fermentation."@en . . "Grape must"@en . "Grape or wine must is the juice pressed from grapes before it has fermented; new wine. Grape must is also used in making traditional balsamic vinegar, which must mature by a long and slow process thought natural fermentation."@en .