Sweetness

Sweetness is the sweet taste you experience in a wine, and it comes first and foremost from the sugar that remains in the wine after fermentation. During fermentation the yeast converts the sugar in the grapes into alcohol, but if the process stops, or if the grapes were very sugar-rich to begin with, some residual sugar is left behind. It is this residual sugar that you perceive as sweetness. Wines are typically classified by their degree of sweetness, from dry through off-dry and medium-sweet to sweet, and sweet wines such as dessert wine can have a fairly high sugar concentration achieved through, for example, late harvest, noble rot, drying the grapes or the addition of grape spirit.

Sweetness matters a great deal for how a wine tastes and how it pairs with food. An important point is that acidity and sweetness work together: a fresh acidity lifts a sweet wine and keeps it from seeming cloying, while sweetness in turn tempers acidity, bitterness and astringency. That is why a wine with noticeable residual sugar can still come across as balanced and lively.

You can often sense the sweetness before your first sip, because sugar makes the wine more viscous and produces more pronounced "legs" or tears on the inside of the glass. Be aware, though, of a common misunderstanding: a wine with high alcohol can give a warm, almost sweetish sensation on the tip of the tongue without containing any appreciable sugar. Learn to tell that warmth apart from genuine sweetness.