When people talk about wine sweetness, they may be talking about one of two different things: The first is the residual sugar (RS for short) in the wine, while the second is the perception of sweetness.
Whether it’s red, rosé, or sweet white wine, the measurable sweetness level of a beverage comes from its residual sugar, referring to the natural fruit sugars (glucose and fructose) that remain in the final product after fermentation has occured. Wine fermentation, the process in which grape juice turns into wine, involves either added or natural yeasts eating up the grape sugars and expelling alcohol. Different yeast strains eat sugar at different rates, leaving more or less residual sugar. Other factors that can stop or slow the fermentation process early include the rise in alcohol, which eventually overwhelms yeast, the presence of more complex sugars that are harder for the yeast to consume, or the addition of sulfur.
Residual sugar is typically measured in grams per liter of wine (g/L for short), so sweet wines have a higher RS number and dry wines a lower RS number. Moscato wine, for example, often has an RS between 40-100 g/L while Pinot Grigio might have 0-20 g/L.
Learn more about sweet wine types from around the world.
Residual sugar level will certainly have an effect on how the palate perceives sweetness, but it is not the only factor when it comes to how something tastes. Along with the actual sugar content, a higher alcohol level can enhance the sense of sweetness in a wine. Conversely, acidity and tannins will cause a wine to seem less sweet. Likewise, flavors or aromas we associate with sweetness, like fruity or floral notes, can enhance the perception of sweetness. In creating a balanced wine, whether sweet or dry on the wine sweetness chart, winemakers should strive to balance the factors of residual sugar, alcohol, acid, and tannins to create a pleasing beverage. The best way to learn more is to drink sweet wine and try pairing it with food. You’ll discover how many sweet wine types actually exist, and which ones suit your palate and personal preferences.