Dessert wines are traditionally made from grapes harvested late in the season. This allows extra sugar to accumulate in the juice but results in a much lower yield — one reason why stickies can be expensive. Wine is usually fermented until it’s ‘dry’ — meaning that almost all the sugar in the juice (winemakers call it ‘must’ at this stage) has been converted into alcohol by yeast fermentation.
Fermentation stops when the alcohol level reaches about 14% — the yeast stops growing because it’s effectively pickled. Because of the extra sugar in the juice used for dessert wines, there’s enough sugar left after fermentation to give them their characteristic body and sweetness.
Often the high sugar concentration causes fermentation to stop at lower alcohol levels. Even a medium-sweet table wine has a sugar content of no more than about 3%, whereas a dessert wine is typically 10%–20% sugar.
Stickies are very different from fortified wines, such as port or muscat. Fortified wines are made by adding spirit to part-fermented wine to pickle the yeast while there’s still unfermented sugar. Their alcohol content is typically 15%–20%. Australian dessert wines fall into two groups:
Late harvest The grapes are harvested when the berries have dried and shrivelled on the vines in late autumn. There’s little juice but the sugar can be 35% of the weight of the grape.
Botrytis-affected styles The botrytis also contributes flavour notes of its own, which give these wines their special appeal. But the degree of botrytis infection can vary, so there isn’t always a clear distinction between late harvest and botrytis-affected styles.
Three of the wines in our test were imported ‘ice wines’ (Eiswein in German). This style of wine is a speciality of regions that get really cold late in the season, such as Germany, Austria and Canada. The grapes are picked and pressed while frozen, sometimes at night. The ice crystals in the part-frozen juice contain very little sugar and remain with the skins, pips and other solids, leaving a concentrated juice that contains as much as 30% sugar.
This method also concentrates the acid in the juice. It’s the much higher acidity of ice wines (compared with late harvest) that gives them their characteristic refreshing sweetness. Two of the ice wines in our test were produced in New Zealand by simulating this process using refrigeration.
Experts recommend serving dessert wines slightly chilled rather than straight from the fridge. And because you don’t drink as much of them as other wines they should be served in a smaller glass, such as a sherry glass. It’s also preferable that the glass is tulip-shaped to capture the fruity aromas and acidity that balance the wine’s sweetness.
Steer clear of heavy desserts (especially chocolate); dessert wines are best with fresh fruit or lighter desserts such as a lemon tart, caramelised pears or crème brûlée. And there’s nothing wrong with serving a dessert wine as an aperitif with blue or soft cheeses or a pâté.