How Residual Sugar Occurs
When yeast converts all available sugar to alcohol, the wine is fermented to dryness. Residual sugar remains when:
- Fermentation is stopped intentionally — by chilling, fortification (adding spirits), or filtration
- Yeast reaches its alcohol tolerance — typically 14-16% ABV
- Stuck fermentation — yeast dies before completing its work
Sugar Levels and Perception
| Style | RS (g/L) | Examples |
|---|---|---|
| Bone dry | 0-1 | Muscadet, Chablis |
| Dry | 1-4 | Most reds, Sauvignon Blanc |
| Off-dry | 4-12 | Riesling Kabinett, some Chenin Blanc |
| Medium sweet | 12-45 | Gewürztraminer, Moscato d'Asti |
| Sweet | 45-100+ | Sauternes, Tokaji, Ice Wine |
The Role of Acidity
High acidity can mask residual sugar, making a wine taste drier than its RS would suggest. German Riesling is a perfect example — wines with 30+ g/L RS can taste balanced and refreshing because of their soaring acidity.