To produce this “liquid gold”, grapes are left on the vine until sub-zero temperatures of -8°C (17.6°F) or lower are reached. This typically occurs sometime between November and February. While hanging on the vine, flavours continue to develop and the grapes dehydrate, concentrating the remaining juice.
When preparing for an Icewine harvest, grapegrowers and winemakers keep a close eye on the weather. Ideally, they will send their pickers out once the temperatures have sustained -10°C (14°F) or lower for several hours. Because the temperatures are usually coldest at night, Icewine pickers often have the arduous task of harvesting by moonlight. Once picked, the grapes need to remain frozen at a temperature below -8°C (17.6°F) until they are pressed.
When the grapes are pressed, the water is left behind as ice and a very small amount of concentrated juice is extracted. On average, Icewine yields only 15% of the expected yield for table wines. The resulting juice is extremely sweet and can be difficult to ferment because of the cold temperatures and high sugar content.
The Wines of Marked Quality Regulation governs the production of BC VQA Icewine. In addition to the temperature regulations (harvesting at or below -8°C), the pressed juice and must is required to have a minimum of 35 Brix (a measurement of sugar). Artificial refrigeration of grapes, juice, must or wine is strictly prohibited.