Icewine is a type of dessert wine produced from grapes that have been frozen while still on the vine. The sugars and other dissolved solids do not freeze, but the water does, allowing for a more concentrated grape juice to develop. The grapes' must is then pressed from the frozen grapes, resulting in a smaller amount of more concentrated, very sweet juice. With icewines, the freezing happens before the fermentation, not afterwards. Unlike the grapes from which other dessert wines are made, such as Sauternes, Tokaji, or Trockenbeerenauslese, icewine grapes should not be affected by Botrytis cinerea or noble rot, at least not to any great degree. Only healthy grapes keep in good shape until the opportunity arises for an icewine harvest, which in extreme cases can occur after the New Year, on a northern hemisphere calendar. This gives icewine its characteristic refreshing sweetness balanced by high acidity. When the grapes are free of Botrytis, they are said to come in "clean". This results in a very complex and sweet wine. Much icewine is made from the grapes Riesling, Vidal, Cabernet Franc and Cabernet Sauvignon, but there is also icewine made from Shiraz, Merlot, Sangiovese and others.
Grapevines in Luxembourg being grown for ice wine
Ice wines produced from the Niagara College Teaching Winery
Monument commemorating the first harvest of ice wine in Bingen in 1830
Icewine grapevines at Inniskillin. The winery was the first in Canada to produce icewine for commercial purposes in 1984.
Trockenbeerenauslese, or TBA, is a German botrytized wine made entirely from the individually selected grapes fully "dried" from Botrytis cinerea, hence the name. Trockenbeerenauslese is a very sweet wine, highest among the wines of the QmP category that includes also Auslese and Beerenauslese.
Botrytized grape cluster