Icewine Evolution: Freeze on the vine, or try the freezer

by Garrett Heaney

Karl Kaiser is co-founder of Inniskillin Wines of Niagara, Ontario. He was born in Austria and attended a monastery school where winemaking and viticulture was a tradition. He later received his B.S. in Chemistry and Bio-Chemistry at Brock University in St. Catharines, Ontario in 1974. While at school, 

Karl began buying vines and making his own wine, which led him to meet his future partner, Donald Ziraldo, at Ziraldo Nurseries.
 
Inniskillin produced its first vintage of icewine in 1984. Because Canada is blessed with cold winters, I thought it an appropriate climate to make icewine. Icewine was first made by the Germans, who called it eiswein.    

Icewine owes much of its uniqueness to a high level of acidity which gives balance to the concentration of sugar in the grapes. Wines from cooler climates are characteristically higher in acids and highly aromatic.

The production of icewine is suited to the climate conditions of Canada’s Niagara Peninsula. Soils on the Niagara Peninsula are generally deep and obtain a considerable amount of essential minerals from different types of bedrock.

Our icewine is produced from French hybrids such as Vidal. Vidal works particularly well because of its thick skin. Vitis vinifera grapes like Riesling and Cabernet Franc are also good, but any late-ripening grape with good acidity works well for icewine. We grow from April into December or January. The repeated freezing and thawing causes the grapes to dehydrate, thus concentrating the sugars and acids in the juice and intensifying the flavor. 

Due to its high levels of sweetness and high cost of production, icewine is typically packaged into thin, 375-mL bottles known as splits. While other wine styles can be found in similar sized half-bottles, icewine is almost always found in the tall, high-necked “Bellissima-style” bottle shown here. 

The grapes, having already reached full ripeness in October, are left untouched on the vines under a cloak of protective netting (to keep the birds from eating the sweet grapes) until the first deep freeze of the Canadian winter. The harvest takes place between December and January, at 22–25 ºF (–9 to –13 °C).   

The grapes are either handpicked or machine harvested in their naturally frozen state, usually during the night. Despite the protective netting, wind damage and ravaging birds can further reduce the very low yields, sometimes as little as five to ten percent of a normal yield.

After the frozen grapes have been harvested, they are pressed while still frozen — the winery doors are left open to maintain the sub-zero temperature. The water in the juice remains frozen as ice crystals during the pressing and only a few drops of sweet concentrated juice are obtained from each grape.   

After racking (and clearing the sediment), the clear juice is inoculated with a strong yeast culture. The juice ferments very slowly for several weeks, sometimes even months while aging. It ceases fermenting naturally at approximately 10–12 % alcohol by volume.

By VQA (Vintners Quality Alliance) standards  residual sugar must be a minimum of 125 grams per liter (g/L). Inniskillin’s icewine averages between 150 to 250 g/L.