Juice obtained by pressing (pressing) grapes; colloquially also called must. This is the untreated product immediately after pressing; it could also be called "cloudy grape juice". In terms of wine law, there is a difference to grape juice. The latter is only produced by further treatment of grape must by making it durable against further fermentation. It is also the starting material for the preparation of wine, sparkling wine, concentrated gra pe must, RCGM (rectified grape must concentrate) and verjus. Grape must is permitted for sweetening in compliance with wine legislation. See regarding the different preliminary stages of wine (such as Beaujolais Paradise, Federweißer or Sturm) under must. The unit of measurement used to represent the relative density or specific gravity of grape must (colloquially the sugar content) is called must weight.
For me, Lexicon from wein.plus is the most comprehensive and best source of information about wine currently available.Egon Mark
Diplom-Sommelier, Weinakademiker und Weinberater, Volders (Österreich)