How are sweet wines made? Five methods, one secret: balance.

Why sweet wine is all about balance

Sweet wines have been made since ancient times, but their popularity has risen and fallen. The real challenge for the winemaker is always the balance between sugar and acidity. Without enough acidity a sweet wine tastes cloying; with it, the wine feels fresh and can last for decades. Susie shows a Rivesaltes from 1945 to prove the point.

There are two broad routes. Sugar can be kept in the wine by stopping fermentation, or added after fermentation, as with some Sherries and sweeter sparkling wines. Or the grapes themselves can be naturally concentrated before fermentation, by late harvesting, noble rot, freezing or drying.

Fortification and late harvest

In fortified sweet wines, grape spirit is added during fermentation. The alcohol kills the yeast and leaves natural sugar behind. Port works this way, and so do France's vins doux naturels such as Muscat de Beaumes-de-Venise, Banyuls and Rivesaltes, despite a name that suggests nothing is added. Moscatel de Setúbal from Portugal is another example.

For late harvest wines, grapes stay on the vine after full ripeness and begin to shrivel, losing a large part of their water. This is called passerillage. Look for Spätlese and Auslese in Germany, Vendange Tardive in Alsace and Vin de Constance in South Africa. Riesling, Sémillon and Chenin Blanc are favorite grapes.

Noble rot: Sauternes, Tokaji and TBA

Botrytis cinerea, or noble rot, thrives where misty mornings give way to warm, sunny afternoons, often near rivers and lakes. The fungus pierces the skins, water evaporates, and the grapes shrivel into concentrated berries full of sugar and acid. Sauternes, made from Sémillon, Sauvignon Blanc and Muscadelle where the cool Ciron meets the Garonne, shows apricot, honey, marmalade and marzipan.

In Hungary, Tokaji Aszú is made by adding a paste of botrytized berries to must or base wine. Sweetness was traditionally measured in puttonyos, but since 2013 Aszú is defined by residual sugar. Rare Eszencia, made only from the free-run juice of Aszú berries, ferments for years to very low alcohol and is traditionally served from a spoon. In Germany and Austria, Beerenauslese and the even sweeter Trockenbeerenauslese are made from individually picked overripe and botrytized berries.

Ice wine and dried grapes

For ice wine, healthy grapes are left on the vine until they freeze in winter. When pressed, the ice stays behind and only a tiny amount of very sweet juice runs out. The wines are low in alcohol with vibrant acidity, and the method is used in Germany, Austria and, most often, Canada.

The oldest method is drying grapes after picking, either in the sun or hung in airy lofts, as for Tuscan Vin Santo. For Vin Santo, the dried grapes are pressed after months of drying and the wine is then aged for years in small barrels, developing nutty, caramel and dried fruit notes. Some dried-grape wines, such as Recioto, may also contain botrytized grapes.

The experiment: pairing sweet wine with food

Can sweet wine go with popcorn? The hosts test winemaker Gerhard Kracher's favorite match, salty popcorn with Trockenbeerenauslese, then work through classics: Roquefort with Sauternes, strawberries and cream with Beerenauslese, and chocolate mousse with a lightly chilled Banyuls. The golden rule: your wine should be at least as sweet as the food.

They also compare a Kracher Beerenauslese and Trockenbeerenauslese side by side, dip cantuccini into Fontodi's Vin Santo, and taste two sweet wines blind before a Vietnamese caramelized pork dish proves that sweet wine is not just for dessert. Spotting botrytis character is a useful skill that helps you prepare for WSET Level 3.