residual sugar (RS)

The natural grape sugar that is either unfermented at the end of the fermentation process or added back into the wine, as with a dosage added to a sparkling wine. In some cases, there is so much natural sugar that fermentation can't complete its process, as is the case with some dessert wines like Germany's trokenbeer­enauslese. In other instances, fermentation is purposefully arrested by adding a soupçon of sulfur dioxide which inhibits the yeast, or by adding alcohol (as is done with fortified wines), which raises the alcohol to a level (15 to 16 percent) above which the yeast cannot work. dry wines may have little residual sugar (0.1 to 0.2 percent), semisweet wines usually range from 1 to 3 percent, and late harvest wines may range as high as 28 to 30 percent. Residual sugar is sometimes referred to as reducing sugar or by the initials RS.