How sweet or dry a wine appears, depends among other things, on the acidity of the wine. The acidity contributes significantly how we judge the sweetness of a wine. In the case of two wines with the same residual sugar content, usually the wine eith more acidity appears less sweet. Our impression not necessarily has to match with the classification of a wine as dry, semi-dry, sweet or sweet. This classification is regulated by legal requirements, with the residual sugar playing an essential role.
The classification for medium sweet and sweet wines is exclusively based on the residual sugar content. Medium sweet wines have a residual sugar of more than 18 grams not exceeding 45 grams per liter while sweet wines must show at least 45 grams of residual sugar per liter. For the classification of semi-dry and dry wines, in addition to the residual sugar, the total acidity plays a role. Dry wines may contain a maximum of 9 grams of residual sugar per liter. However, if the residual sugar content is greater than 4 grams per liter, the total acid of the wine has to be not more than 2 grams below the residual sugar content. Therefore, a wine containing 9 grams of residual sugar must contain at least 7 grams of acid per liter. Medium dry wines have a residual sugar that exceeds the values set for dry wines and they may have up to 12 grams of residual sugar per liter. At values between 12 and a maximum of 18 grams of residual sugar per liter, the total acid per liter may not be more than 10 grams lower than the residual sugar content. In the case a wine contains 18 grams of residual sugar, the total acid therefore has to be at least 8 grams.
More information about the sweetness of other types of wine can be found in the Mainmenu in the articles of the different wine types, such as Sherry, Port, Madeira, Moscato d’Asti and others.