Is "ice wine" really made from frozen grapes?

Dear Dr. Vinny,

I was in Vermont recently and stopped by a local winery. They were selling “ice wine,” which is made from frozen grapes. Is there anything special about making a dessert wine from frozen grapes?

—Jonah D., Los Angeles

Dear Jonah,

Ice wine is an unusual type of dessert wine that’s made by letting grapes stay on the vine long after a traditional harvest, waiting to pick them until the weather gets cold enough that they freeze. It’s a stressful, expensive process, but if you can pick the grapes and crush them while they’re still frozen, the frozen part—the water content—will be left behind, and what’s extracted is extremely sweet and concentrated.

You may have heard of ice beer, which undergoes a similar process in which it’s chilled down to a point where ice crystals form and are filtered off, leaving a higher-alcohol product behind. Ice wine, however, doesn’t necessarily have higher alcohol—after all, to keep it sweet, not all of the grape sugar is converted to alcohol.

Making ice wine is a pretty precarious process. The longer you leave the grapes on the vine, the more risk they run of birds, disease, rain, hail and mold. Then you have to cross your fingers that they gets cold enough to freeze, and when they’re frozen you have to work quickly. By the time the shriveled, frozen grapes are pressed, very little juice comes out. But what comes out is rich and sweet, like drinking honey.

There’s a way to bypass some of the risk by picking the grapes and then freezing them. These are sometimes referred to as “icebox” wines.

—Dr. Vinny