The residual sugar is also known as residual sugar (short RZ) or sugar residue designated amount of sugar in the wine in g / l , after the natural end of the fermentation is maintained or her targeted stopping. This interruption of fermentation is possible by cooling, by adding sulfur or alcohol and by filtration . The residual sugar is usually referred to as fermentable sugar on official reports from the wine testing institutes and on test results from wine laboratories . The residual sugar consists essentially of fructose (fruit sugar), because the glucose (grape sugar) is converted more quickly into alcohol and carbon dioxide , as well as from non-fermentable types of sugar (see under pentoses ). The indication of residual sugar also includes an amount of sugar added to the wine through a sweet reserve .
The taste of the wines is given in the categories dry , semi-dry , sweet or semi-sweet and sweet . The amount of residual sugar in each category is precisely regulated by wine law. Since it is a voluntary label, the taste information can be given on the wine label .
Usually the residual sweetness does not fall below 0.5 g / l. With ideal fermentation conditions (temperature-controlled fermentation), a wine can ferment down to a residual sugar content of 0.0 g / l, which can no longer be detected. However, such complete fermentation only takes place in individual cases, for example:
- 1993 Retzbacher Benediktusberg, Müller-Thurgau QbA, Kuhn brothers winery, Retzbach - RZ: 0.0 g / l
- 1998 Nordheimer Vögelein , Ortega Kabinett, Hermann Neubert Winery, Nordheim am Main - RZ: 0.1 g / l
- 2006er Zeiler Kapellenberg Dornfelder Spätlese, Erich Martin winery, Zeil am Main - RZ: 0.0 g / l
- 2012 Randersacker Sonnenstuhl Silvaner Spätlese, Winzerhof am Spielberg, Randersacker - RZ: 0.0 g / l
Diabetics can - after consulting their doctor - enjoy a semi-dry wine if the residual sugar consists mainly of fructose and is individually dependent on sugar.