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.
Riesling is a white grape variety that originated in the Rhine region. Riesling is an aromatic grape variety displaying flowery, almost perfumed, aromas as well as high acidity. It is used to make dry, semi-sweet, sweet, and sparkling white wines. Riesling wines are usually varietally pure and are seldom oaked. As of 2004, Riesling was estimated to be the world's 20th most grown variety at 48,700 hectares, but in terms of importance for quality wines, it is usually included in the "top three" white wine varieties together with Chardonnay and Sauvignon blanc. Riesling is a variety that is highly "terroir-expressive", meaning that the character of Riesling wines is greatly influenced by the wine's place of origin.
Ripe Riesling grapes in Rheingau, Germany
A Kabinett-level German Riesling from the Mosel
A German Riesling from the 1975 vintage, an Erbacher Siegelsberg Kabinett from Schloss Reinhartshausen in Rheingau, uncorked at 32 years of age in 2007. It shows the typical golden to amber colour of aged Riesling, which is shared by many other aged white wines.
A bunch of Riesling grapes after the onset of noble rot. The difference in colour between affected and unaffected grapes is clearly visible.