Wine Chemistry 101: pH, Acidity, and Sulfites Explained

Updated: February 2026 | Reading Time: 14 minutes

Great winemakers understand chemistry. While you don't need a degree in biochemistry to make good wine, understanding the fundamental chemical properties of wine helps you make better decisions and troubleshoot problems when they arise.

In this guide, we'll explore three critical chemical properties: pH, acidity (TA), and sulfites. Understanding these three factors alone will dramatically improve your winemaking.

Understanding pH

pH is a measure of how acidic or basic a solution is, on a scale from 0 to 14. A pH of 7 is neutral; below 7 is acidic, above 7 is basic (alkaline).

In winemaking, pH typically ranges from 2.9 to 4.0, with most wines falling between 3.0 and 3.8. This is important because pH affects nearly everything about wine: color, stability, aging potential, and microbial safety.

Why pH Matters

Microbial Stability: Lower pH (more acidic) wines are more resistant to bacterial spoilage. Bacteria prefer higher pH environments. A wine with pH below 3.5 is generally safer from bacterial problems.

Color: At lower pH, anthocyanins (the pigments in red wine) are more vibrant and red. At higher pH, wines appear more blue and purple, and colors can fade faster.

Sulfite Effectiveness: Sulfites are more effective at lower pH. At pH 3.5 and above, you need more sulfites to achieve the same protective effect.

Oxidation: Lower pH wines resist oxidation better than higher pH wines.

Taste: pH directly affects how acidic wine tastes. However, pH and perceived acidity don't always align—other factors play a role.

Understanding Titratable Acidity (TA)

While pH measures the strength of acids, TA measures the total amount of acid present in your wine. TA is expressed as grams per liter (g/L) of tartaric acid equivalent.

Most wines have a TA between 4 and 8 g/L, though this varies by style:

The Relationship Between pH and TA

pH and TA are related but not the same. You can have wines with high TA but higher pH (often in hot climates where grapes ripen quickly, losing acidity but retaining some residual acids). Conversely, you can have wines with lower TA but lower pH (cool-climate wines with more balanced acidity).

The ideal balance varies by wine style, but most winemakers aim for:

• White wines: pH 3.1-3.3, TA 6-8 g/L
• Red wines: pH 3.3-3.6, TA 5-6.5 g/L

Measuring and Adjusting Acidity

You can measure pH with a digital pH meter (more accurate) or pH strips (less accurate but workable). TA is measured through titration, typically with a test kit.

If your acidity is too high:

• Blend with lower-acid wine
• Use malolactic fermentation to reduce acidity
• Wait—acidity often decreases naturally during aging

If your acidity is too low:

• Add acid (tartaric acid is most common)
• Harvest grapes earlier for higher acidity
• Avoid malolactic fermentation

Understanding Sulfites

Sulfur dioxide (SO₂), commonly called "sulfites," is the most widely used preservative in winemaking. It's been used for thousands of years and remains essential to modern winemaking.

What Sulfites Do

Antioxidant: Sulfites bind to oxygen, preventing the browning and flat flavors caused by oxidation.

Antimicrobial: Sulfites inhibit the growth of wild yeast and bacteria that can spoil wine.

Clarification aid: Sulfites help wine clear more quickly.

Free vs. Bound Sulfites

Total sulfites in wine include both "free" and "bound" forms. Only free sulfites provide the protective benefits. When you add sulfites, only a portion becomes free; the rest binds to acetaldehyde, sugars, and other compounds.

The ratio of free to bound sulfites depends on pH:

• At pH 3.0: About 50% is free
• At pH 3.5: About 25% is free
• At pH 4.0: About 10% is free

This is why higher-pH wines need more sulfites—they need more total sulfites to achieve the same level of free sulfites as lower-pH wines.

Common Sulfite Levels

When to Add Sulfites

At crush: Adding sulfites to must helps protect against oxidation and wild yeast. This is common for whites and some reds.

At fermentation end: Some winemakers add a small amount to protect the wine while it clears.

After malolactic fermentation: Adding sulfites after MLF stops the fermentation and protects the wine.

At bottling: Final sulfite addition protects the wine in the bottle.

Putting It All Together

These three factors—pH, TA, and sulfites—interact in complex ways. Here's how they relate:

• Low pH + adequate sulfites = stable wine
• High pH + low sulfites = unstable, oxidation-prone wine
• High TA + low pH = crisp, bright, stable wine
• Low TA + high pH = flat, potentially problematic wine

When troubleshooting wine problems, start by checking these three parameters. Most issues can be traced back to one or more of these factors being out of balance.

Testing Your Wine

Essential tests for winemakers:

• pH: Digital pH meter for accuracy
• TA: Titration test kit
• Sulfites: Ripper or aspiration test kit

At minimum, test your wine at these stages:

1. At crush/juice preparation
2. At fermentation completion
3. After malolactic fermentation
4. Before bottling

Conclusion

Understanding wine chemistry—particularly pH, acidity, and sulfites—gives you unprecedented control over your winemaking. These three factors affect everything from fermentation to aging to final flavor. The good news is that testing is straightforward and the relationships are well-understood.

You don't need to become a chemist to make great wine, but having a basic understanding of these principles will make you a better, more confident winemaker.

Ready to learn how to follow a recipe? Read How to Read a Wine Recipe or Formulation