Can Grapes Freeze Before a Harvest?

Ice Wine

• Ice wine, a sweet dessert wine similar to Moscato or Riesling, originated in the Alsace region of Germany. Sometimes spelled eiswein, the name aptly reflects how it's made. While other wines bear the name of the grape varietal, ice wine grapes actually freeze before harvest. While it's produced in America, Germany, Austria and Slovenia, the northwest region of Canada has been praised for producing some of the finest ice wines.

Origin

• There is no doubt that fate met serendipity one cold night in an orchard in Germany when an early frost ruined the harvest. Fearful of financial loss, the winemaker went ahead and harvested the grapes early in the morning, processing them and selling to great reviews, possibly as recently as the late 1800s. The technique was refined into the process used to deliberately create ice wine. Grapes destined for this honor are left on the vine well into December, possibly January, anticipating a deep enough frost.

Science Behind Technique

• The sweet depth of flavor exhibited in ice wine results from dehydration caused by sun exposure and the compounds manufactured inside the grape after the vine has gone into its dormant winter state. Harvesting frozen grapes can be done at night to ensure they don't thaw before pressing; the optimal temperature is about 17 degrees Fahrenheit. The frozen water stays in the press as ice crystals while the juice collected is sweet, acidic and aromatic with a high sugar content.

Vintage Ice Wine

• The technique for making ice wine has been refined, and some wineries even cryo-extract, meaning they freeze the grapes to mimic the weather. The process helps separate less sweet grapes, which freeze before the more sugar-rich ones. Some producers think the high sugar and acid content will allow the wine to keep indefinitely, though only time will tell. While Germany is noted as the originator of ice wine, British Columbia is now the top producer. Cold winters and strict guidelines by the Vintners Quality Alliance have made Canada an ideal place to produce the prized wine.