Fungus and Ice Make the Naturally Sweetest Wines
Broadly speaking, there are three types of sweet wines. There are fortified wines to which a neutral brandy has been added to stop fermentation early in its process, thereby retaining residual sugar from the grape juice in the finished wine. There are wines to which sugar has been added post-fermentation during the production process, and there are naturally sweet wines.
How are naturally sweet wines produced?
Naturally sweet wines are produced by one of two methods. The methods are:
- freezing the grapes
- using grapes that are affected by a fungus known as botrytis
Removing water from grapes is key
The key to making non-fortified sweet wines is removing water from the grapes so that only a highly-concentrated sweet "syrup" is extracted from the grape when pressed. Each of the two methods used removes the dilutive effect of water that is present in pre-pressed grapes, leaving behind grape “must” of high sugar content that is then made into wine. Freezing the grapes traps water as ice. The botrytis fungus shrivels the grape, causing it naturally to lose water.
Pressing grapes to make dessert wines is a famous practice in Canada and Germany
Pressing frozen grapes to make sweet wine is a famous practice of the Canadians (Ice Wine) and Germans (Eiswein). The regions where these sweet wines are produced are cool climates that facilitate natural freezing of the grapes while they are still on the vine. The frozen grapes are picked at ideal temperature and immediately pressed to make wine.
Fungus-affected grapes produce sweet dessert wines of world renown
Botrytis, a natural fungus that causes the grape to shrivel while still on the vine, is much desired in regions of Europe that produce sweet wine, namely Sauternes in France and certain areas of Germany.
Unfortunately, botrytis does not happen every year (usually only two to three times per decade), but when it does, botrytis-affected grapes are pressed and made into some of the most expensive and highly-sought-after dessert wines.
"Pressing frozen grapes to make sweet wine is a famous practice of the Canadians (Ice Wine) and Germans (Eiswein)."
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