The Science of Sugar in Wine: Residual Sugar (RS)
All wine contains sugar, a natural component of the grapes from which it is made. The level of sweetness in the final product is determined by what is known as 'residual sugar' (RS). During the winemaking process, yeast ferments the grape juice, consuming the natural sugars (glucose and fructose) and converting them into alcohol and carbon dioxide. The fermentation can be stopped early by the winemaker to leave more sugar behind, resulting in a sweeter wine. Conversely, allowing the fermentation to complete results in a 'dry' wine with very low residual sugar.
Key Factors That Influence Residual Sugar
Several elements contribute to a wine's final sugar content beyond the basic fermentation process:
- Grape Ripeness: The sugar concentration in grapes increases as they ripen. Grapes from warmer climates or those left to ripen longer will have higher initial sugar levels. This gives the winemaker the potential to produce either a higher alcohol wine or a sweeter one.
- Winemaker's Intervention: A winemaker can halt the fermentation process using techniques like chilling the must or adding alcohol (fortification), which preserves unfermented sugars. This is commonly done for dessert wines.
- Yeast Type: Different yeast strains have varying tolerances to alcohol and sugar. The chosen yeast affects how much sugar is consumed during fermentation.
Dry, Off-Dry, and Sweet: Understanding Wine Sweetness Categories
Wine sweetness is categorized based on the amount of residual sugar (RS) measured in grams per liter (g/L). This is the critical distinction for sugar content, much more so than whether the wine is red or white.
- Dry Wines: These wines contain very little residual sugar, typically less than 10 g/L. The vast majority of the grape sugars have been converted to alcohol. Most popular red wines (like Cabernet Sauvignon, Merlot, Pinot Noir) and many white wines (like Sauvignon Blanc, Chardonnay, Pinot Grigio) fall into this category. Per 5-ounce glass, dry reds average about 1 gram of sugar, and dry whites average about 1.4 grams.
- Off-Dry Wines: With a noticeable but not overpowering sweetness, these wines usually have between 10 and 30 g/L of RS. Some Rieslings, Gewürztraminers, and certain Rosés can be off-dry. A 5-ounce serving might contain between 1.4 and 5 grams of sugar.
- Sweet Wines: These wines have substantial residual sugar, generally exceeding 30 g/L, and can go much higher. They include late-harvest wines and some Moscatos. Sugar content per 5-ounce glass can range from 5 to 18 grams.
- Dessert Wines: These are the sweetest wines, often fortified to stop fermentation early and preserve high sugar levels. RS levels are frequently above 45 g/L and can exceed 100 g/L. Examples are Port, Sherry, and Sauternes. A 5-ounce pour can contain 8 grams of sugar or more, sometimes rivaling the sugar content of soda.
Sugar Content Comparison Chart (per 5-ounce glass)
This table provides average sugar content for different wine types. Actual values can vary.
| Wine Type | Average Sugar (grams) | Typical RS Level | Sweetness Level |
|---|---|---|---|
| Dry Red Wine | ~1 g | < 10 g/L | Dry |
| Dry White Wine | ~1.4 g | < 10 g/L | Dry |
| Off-Dry Wine | 1.4 – 5 g | 10 – 30 g/L | Slightly Sweet |
| Sweet Table Wine | 5 – 18 g | > 30 g/L | Sweet |
| Sweet Dessert Wine | 8+ g | > 45 g/L | Very Sweet |
| Brut Sparkling Wine | < 1 g | < 12 g/L | Dry |
Choosing Wines with Lower Sugar Content
For those mindful of sugar intake, focusing on the wine's dryness level is key. Here's how to make informed choices:
- Prioritize Dryness: Always opt for wines labeled 'Dry.' Sweetness descriptors on labels (like 'sweet,' 'semi-sweet,' or 'doux') signal higher sugar.
- Understand Sparkling Wine Labels: For sparkling wines, look for 'Brut Nature,' 'Extra Brut,' or 'Brut.' These terms indicate very low to low sugar levels, with 'Brut Nature' being the driest. 'Extra Dry' or 'Sec' actually contain more sugar than 'Brut'.
- Consider Alcohol Percentage: Wines with a higher alcohol by volume (ABV), typically 13.5% or higher, often indicate that more sugar was converted to alcohol, resulting in a drier wine.
- Know Your Varietals: Certain grape varietals are typically made into dry wines. For red, choose Cabernet Sauvignon, Pinot Noir, or Merlot. For white, opt for Sauvignon Blanc, Pinot Grigio, or unoaked Chardonnay. Be aware that some wines made from typically dry grapes, like Zinfandel or Riesling, can be made in sweeter styles depending on the producer and region.
Examples of Typically Low-Sugar Wines:
- Dry Reds: Cabernet Sauvignon, Pinot Noir, Merlot, Sangiovese, Cabernet Franc
- Dry Whites: Sauvignon Blanc, Pinot Grigio, Albariño, Unoaked Chardonnay, Grüner Veltliner
- Dry Sparkling: Brut Nature Champagne, Extra Brut Cava, Brut Prosecco
Conclusion
To answer the question of what has more sugar, red or white wine, the difference between dry red and dry white table wines is quite small, with dry whites holding a slight edge on average. However, this distinction is far less important than the wine's sweetness level, determined by its residual sugar. Dry wines of any color are significantly lower in sugar than off-dry, sweet, or dessert wines. By understanding how residual sugar affects sweetness and paying attention to label terms and varietals, you can easily select wines that align with your dietary preferences, whether you prefer red or white. To deepen your understanding of wine components and characteristics, explore educational resources like Wine Folly's guide to carbohydrates in wine, which provides detailed information on what goes into your glass.
