Riesling as a sweet wine.This is one of the rare grapes that will make sweet wines which dazzle just as much as its dry ones. The reason is the grape’s piercing acidity, which balances even the most intense sweetness so that a wine with 50 grams (1¾oz) of residual sugar can taste light, refreshing and even delicate.

Riesling as a sweet wine

Rieslings may be made off-dry or sweet by simply stopping the fermentation (by adding sulphur dioxide, centrifuging the wine or chilling it) or (where the law allows) by adding Süssreserve – sweet unfermented grape juice. The method chosen affects the flavour: the sugar in a ripe grape is composed of roughly equal amounts of glucose and fructose. The glucose ferments before the fructose, so if you stop the fermentation the residual sweetness is fructose – and fructose tastes more fruity and refreshing than glucose. If you ferment the wine to dryness and then add Süssreserve, you don’t gain that extra dimension.

Fine sweet Rieslings are made with the help of Botrytis cinerea, or noble rot, the fungus that shrivels the grapes and concentrates their sweetness and acidity. Botrytis-affected wines usually come from Germany, Austria, Alsace, New Zealand and California. For German growers they are a flagship, though not always a profitable one. An estimate from the Rheingau puts the cost of producing a bottle of Trockenbeerenauslese (TBA) at 255 – around 50 more than its selling price.

Another estimate is that it takes one picker one day to pick the grapes for a single bottle of Beerenauslese, and one picker one day to pick the grapes for half a bottle of Trockenbeerenauslese.

Yet another sweet style is possible where Riesling thrives in cold climates. For Eiswein/Icewine the grapes are picked frozen solid, when the night-time temperature plunges to –6°C (21°F) or lower. These low temperatures may not occur until January, but the wine nevertheless bears the vintage date of the previous year. When the grapes are pressed the water is left behind in the form of ice, and intensely sweet juice runs (very slowly) from the press. Some growers like to have some botrytized grapes in their Eiswein, while others prefer the purer flavours that come from having no botrytis-affected grapes.

Canada produces more Icewine than any other country – even more than Germany. By the late 1990s it made some 50,000 cases a year and brought Canada international attention. Oregon, Michigan and Luxembourg also make some.