Winter in the winemaking calendar is usually a quiet time, a time to relax after a busy period. This is not true for winemakers in the coldest regions of Canada, Germany and Austria. Winemakers here are carefully watching thermometers, waiting for the moment the temperature drops to -8C (20F). When that moment comes, usually at night before sunrise, teams of pickers spring into action and the race is on to harvest bunches of frozen grapes to produce Eiswein in Germany or Ice Wine in Canada.
When a grape freezes, water in the grape is frozen but the dissolved components containing sugars and acidity do not freeze. The frozen water can be separated leaving behind a highly concentrated sugar solution. Wine made from this concentrate is very sweet with a bright acidity. When the grapes freeze, the entire crop must be harvested immediately, if the grapes thaw, they cannot be refrozen as ice crystals will damage the cell walls of the grape and cause it to spoil.
Making ice wine is a gamble. The grapes are on the vine throughout the summer and autumn and a vulnerable. Entire vineyards of ripe grapes waiting for the first hard frost have been devoured by hungry birds, spoilt by rot or damaged by bad weather. Other attempts have failed because the temperature did not drop low enough and the grapes did not freeze.
The resultant wine is worth the effort! The sweet dessert wine delicious and unlike other ‘sticky’ sweet wines. It is highly prized and is usually sold by the half bottle.