The sweetness of most sweet wine comes from the natural sugar from the grapes themselves. Sugar in grapes is converted into alcohol during fermentation to become dry wine (i.e., not sweet). However, if the fermentation process is stopped before it is finished, the wine has some residual sugar, and this is basically how sweet wine is made. The sweetness level of the wine depends on the initial sugar level of the grapes when they were picked and when fermentation was stopped, while the aromas depend on the state of the grapes at the time of fermentation. However, the secret of sweet wine is acidity. The sweeter the wine, the higher the acidity should be – otherwise the wine will be too cloying and heavy. A great sweet wine, no matter how sweet it is, always has a fresh finish that makes you want to take another sip. It is like having honey-lemon water; the acidity of the lemon balances the sweetness of the honey.
Let’s first look at the two most well-known sweet wine styles: ice wine and noble rot wine.
Ice wine is made from healthy grapes that are frozen. The juice in the berries turns into ice, thus concentrating the sugar and flavour. The wine is pure with intense fresh fruit aromas. In Europe, the law states that these grapes can only be picked at –8ºC ,which is often in the middle of the night, therefore only a few countries (such as Germany and Austria) can potentially produce it. However, the weather conditions are not right every year, so ice wine from these countries is rare and often high priced. Canada has more reliable ice wine weather conditions, but there is no law governing the production, so some producers pick the grapes during the normal harvest season and “freeze” them in wineries, a much cheaper and more reliable method to make ice wine than picking the grapes in the dead of winter. This is the reason why some Canadian ice wine is significantly cheaper than ice wine from other countries.
Noble rot sweet wine is made from berries affected by rot. The fungus, called botrytis cinerea, causes the grapes to shrivel, thus concentrating the sugar, acidity and flavour. More importantly, the fungus changes the flavour profile, so noble rot sweet wine is complex with distinctive honey, marmalade and marzipan aromas. Aged wine tends to acquire nut and dried mushroom bouquets. Noble rot only happens when the weather conditions are right – misty or humid mornings followed by sunshine in the afternoons when the grapes are ripening – otherwise the rot turns to an undesirable grey colour.
The level of complexity depends on the amount of rotten berries used in the making of the wine. Not all berries in a bunch develop noble rot at the same level, and winemakers can choose to pick the entire bunch of grapes, consisting of both healthy and rotten grapes, or they may pick only the berries that are affected by the fungus. Since noble rot is weather dependent and is very labour intensive to pick, the wine tends to be more expensive. The better-known noble rot sweet wines are Sauternes from Bordeaux, Beerenauslese (BA) and Trockenbeerenauslese (TBA) from Germany and Austria and Tokaji from Hungary.
These two styles are very different. Think of ice wine as pure Snow White and noble rot wine as the (charming) stepmother. It’s up to you to decide which style you prefer. However, the best sweet wine is the wine made from grapes with natural high acidity to balance the intense sweetness – Riesling and Chenin Blanc are at the top. Vidal, a grape variety used to make Canadian ice wine, has a much lower acidity and the wine can taste like syrup.
Other sweet wine includes late-harvest sweet wine where the grapes are deliberately picked when they are extremely ripe and sweet with or without noble rot grapes. Fermentation is stopped when the balance between alcohol and sweetness is achieved. The wine has rich ripe fruit aromas such as peach, pineapple and tropical fruits.
Sweet wine made from dried grapes, where the grapes are left to dry out for a few weeks to a few months after picking, has pronounced raisin, dried fruit and spice aromas. Italy is the country with the most sweet wine made in this way, including Vin Santo from Tuscany and Recioto from Veneto (sweet red wine). Vin Jaune from France is also made in this way. Again, a good sweet wine made from dried grapes is sweet but also refreshing with supporting acidity.
All the sweet wine mentioned above has an alcohol level between 6–14%. Port, a sweet wine with an alcohol level around 20%, is made by fortification, a process where spirit is added to fermenting wine. We’ll explore this category in the next article.