The Sweetest Things

Each festive season the wine trade gears up to sell us not just the usual reds, whites and rosés, but some more unusual types of wine that find their niche at posh dinners and special occasions. Champagne is one of course, but a real rarity for most wine buyers are sweet dessert wines. These bijou little bottles (often sold in 37.5cl and 50cl sizes) are invariably quite expensive, but can round off a special meal perfectly.

There are various methods by which a wine can end up sweet. These divide into two basic groups: natural methods, where the grapes overripen on the vine thus increasing sugar levels; and interventionist methods, where a battery of clever techniques - most quite ancient - are employed to achieve similar results.

Natural methods

Late-harvest wines
Grapes are simply left hanging on the vine until overripe. Just like bananas in your fruit bowl, there is a stage somewhere on the continuum between perfectly ripe and complete mush, where the fruit is very sweet. If grapes can be picked at this moment normal fermentation will convert most of the natural fruit sugars into alcohol, but sufficient sugar will be left unconverted to give a luscious, sweet wine. Technically this is known as "RS" (residual sugar). Flavour profile: off-dry to sweet, medium bodied, fruity.

Botrytis-affected wines
An extension of the late-harvest technique which is much rarer. In certain areas a mould called Botrytis Cinerea can grow on overripe grapes. Botrytis punctures the skins and allows water content to evaporate. If unchecked this can destroy fruit, but where the climate is just right it results in grapes where the pulp is very sweet and concentrated. When pressed this produces rich, thick, sweet wines. Flavour profile: honeyed, sweet, full bodied, darkly fruity.

Interventionist methods

Drying grapes
Certain wines, like Recioto wines in Italy, PX sherries and Vins de Pailles in France, are made from grapes which are picked at full ripeness, then dried on mats for many months so that they shrivel and turn into raisins. Wine made from raisined grapes is very thick and sweet, usually with a toffee-like flavour. Flavour profile: caramelised, sweet, full bodied, powerful, fruity.

Adding alcohol
This is the method by which fortified sweet wines like Port, Madeira, Muscat de Beaumes de Venise and Australian Liqueur Muscats are made. During fermentation, when only some of the natural sugar has been converted into alcohol, a dose of spirit is added to the tank which immediately stops fermentation (yeast cannot survive beyond a certain concentration of alcohol). The wine immediately becomes very strong, but all that unconverted sugar makes it sweet too. Flavour profile: sweet, full bodied, strong, alcoholic, fruity.

Ice wines
These wines, found in very cool climate areas like Germany, Austria and Canada, are super-late harvest. The grapes are left on the vine into the dead of winter. On a suitably freezing night the grapes are harvested. The water content can then dispelled as ice so that when the grapes are pressed, the juice is exceptionally thick and sweet. Flavour profile: very sweet, full bodied, honeyed, fruity.

Adding unfermented grape juice
This is how certain cheap German wines are made (but not Germany's many wonderful late harvest and botrytised examples). A dry white wine is made, then sweet unfermented grape juice is blended in. Flavour profile: off-dry to sweet, light bodied, fruity, can be cloying.

There are other minor techniques, but all are variations on these basic recipes.

Tom Cannavan, author of the Good Web Guide to Wine and publisher of wine-pages.com