Various methods of concentrating grape must or wine by removing certain substances and/or reducing the pure water content. The oldest form is the drying of grapes, which was already used in ancient times. Today, this is achieved by late harvesting and/or drying on straw mats/reeds and hanging the grapes on racks for longer periods (see Trockenbeerenauslese and Recioto). Osmosis (reverse osmosis, osmotic distillation) utilises different molecular sizes of liquids or the substances they contain.
Other possibilities for concentration are the utilisation of different boiling or freezing points. Low-pressure and low-temperature evaporators are used for this. This concentrates...
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