Science Fair Project Encyclopedia
Ice wine is a type of dessert wine produced from grapes that have been frozen. The sugars and other dissolved solids do not freeze, but the water does, so the result is an unusually concentrated, often very sweet wine. The effect is comparable to the freeze distillation that was traditionally used to make applejack and similar beverages, but in the case of ice wines, the freezing happens before the fermentation, not afterwards. Unlike other unfortified dessert wines, grapes for ice wine tend not to be affected by Botrytis cinera. When the grapes are free of botrytis, they are said to have come in "clean."
The most famous (and expensive) ice wines are German Eisweins, but ice wine is also made in Canada and the United States. Eiswein is part of the QmP category in the German wine classification. Ice wine production in Canada is regulated by the Vintners Quality Alliance .
Natural ice wines require a hard frost (roughly -9 °C, 15 °F) to occur sometime after the grapes are ripe, which means that the grapes may hang on the vine for several months. If a frost does not come quickly enough, the grapes may rot and the crop will be lost. If the frost is too severe, no juice can be extracted. Bird losses and dropped fruit will also reduce yield the longer it hangs on the vine. Since the fruit must be pressed while still frozen, pickers often must work at night harvesting the grapes within a few hours, while cellar workers must work in unheated spaces.
Some winemakers use cryoextraction to simulate the effect of a frost and typically do not leave the grapes to hang for extended periods as is done with a natural ice wine. Perhaps the most famous of these is Bonny Doon 's "Vin de Glaciere" (icebox wine). In Germany and Canada the grapes must freeze naturally to be called ice wine.
Because of the lower yield of grapes and the difficulty of processing, ice wines are more expensive than table wines . The high sugar levels lead to a slower than normal fermentation. They are often sold in half-bottles (375 ml).
Typical grapes used for ice wine production are: Riesling, Seyval , Vidal Blanc , and, interestingly, the red grape Cabernet Franc. Cabernet Franc ice wine is a light pink color, like most rose wines.
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