AccuWeather.com

By Meghan Evans, Meteorologist

Feb 13, 2012; 8:00 AM ET

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Photo of wine from Photos.com.

The unusually mild winter that has been gripping the U.S., is impacting a sweet treat from nature, ice wine.

A sweet, white wine, called ice wine, is made from frozen grapes, and it is becoming more and more popular. It is a special and expensive wine, because of the intensive process that goes into making it.

Making an Ice Wine

"To make a true ice wine... the grapes must freeze on the vine," said Scott Bubb, owner and winemaker for the Seven Mountains Wine Cellars. "Growers look for three consecutive days where the temperature does not exceed 17 degrees" before the grapes are harvested for ice wine.

"Once they get three days, they get crews together and bundle up because they are going out at 2:00 in the morning and they pick the grapes while the temperatures are at their coldest."

Growers put the frozen clusters into a one-ton crusher. The frozen grapes are then pressed for two days.

"They are trying to squeeze juice from a marble, basically," said Bubb. "They are basically squeezing one drop of juice from each single berry... They are getting about 30 to 35 gallons of juice from a ton."

Typically, a ton of grapes would produce 150 gallons of juice, so frozen grapes yield about one fifth the amount of juice.

It is the water in grapes that freezes, so the drop of juice that is squeezed from a frozen grape has a much higher concentration of sugar. Ice wines are sweet, dessert wines because of the higher sugar content.

"The sugar level in the juice is somewhere in the 40 percent range," said Bubb. "We take half of that-- 20 percent-- of that sugar and ferment that to alcohol and retain the other 20 percent as residual sugar that is all natural."

Mild Winter Causes Set-Backs with Ice Wine in U.S., Europe

Ice wine is often made in the northern tier of the U.S., such as the Finger Lakes region of New York, the Erie area of Pennsylvania and Michigan.

Grapes are rotten by the time that central Pennsylvania and areas farther south in the U.S. would be cold enough for grapes to freeze, according to Bubb.

With unusually mild weather gripping much of the U.S. this winter, even areas that are typically cold enough to produce ice wine ran into set-backs.

"Normally we're picking these grapes at the end of December," said Bubb while explaining that the vintage of the wine is decided by when grapes are harvested. The grapes for Seven Mountains Wine Cellars' ice wine are harvested near the Erie, Pa., area.

"This year because of the extremely mild weather, they didn't get the grapes harvested until early January, so there will be no 2011 vintage. This year's product is going to be a 2012 vintage," added Bubb.

Normally, Canada and Germany produce the most ice wine in the world, but a mild start to the winter in Europe also led to some troubles with ice wine producers.

The recent cold wave gripping Europe was welcomed by ice winemakers in southeastern Czech Republic, according to the Associated Press. In the Czech Republic, a temperature of 7 degrees C, or 19 degrees F, is considered cold enough to harvest the frozen grapes.