Dear Dr. Vinny,

What's the difference between ice wine and wine made with noble rot (botrytis)?

—Devyn, Boulder, Colo.

Dear Devyn,

Let's start with a quick primer on dessert wine, because when we're talking about ice wine and noble rot (botrytis), we're talking about those rich, sweet dessert wines made from grapes with very concentrated sugar levels. There are quite a few ways in which the sugar levels in grapes can be concentrated for the purposes of making dessert wines, and ice wine and botrytized wines employ two different methods, both of which fall under the category of late-harvest wines.

Botrytis cinerea, or "noble rot," as it's nicknamed, is a type of mold that dehydrates grapes, thereby concentrating their sugar content. Some of the most renowned dessert wines made from botrytized grapes include those of Sauternes and Barsac in Bordeaux, the TBAs of Germany and Hungary's Tokaji Eszencia.

Ice wine (officially categorized as Eiswein in Germany) is a type of late-harvest dessert wine made from grapes that have frozen on the vine. These grapes can't be harvested until the first hard freeze of the year, which means they sometimes aren't picked until after the new year in the Northern Hemisphere. The grapes are pressed while still frozen, which yields juice with a higher concentration of sugar due to the water in the grapes being frozen. Some winemakers mimic this effect by picking the grapes and then freezing them mechanically (a process known as cryoextraction), sometimes referred to as “icebox” or “iced” wines.

—Dr. Vinny