What Are Sulfites in Wine? PPM, Labels and Limits Explained

What are sulfites in wine?

Sulfites are compounds that contain sulfur dioxide (SO₂). They are part of nearly every wine for two reasons:

1. They form naturally. Yeast produce small amounts of sulfites during fermentation.
2. Winemakers add them. Sulfur dioxide protects wine from spoilage microbes and from oxidation, which is why it has been used in winemaking for a very long time.

What does "total SO₂ in ppm" mean?

Sulfur dioxide in wine is measured in parts per million (ppm), which is like milligrams per liter. Labs report two numbers:

• Free SO₂: the active form that protects the wine.
• Total SO₂: free plus bound SO₂, which has combined with other compounds in the wine.

The total is the number used for labeling and legal limits. It is also a field on every HarvestLink bulk wine listing, so you can filter by a maximum.

What does the US label rule say?

The Alcohol and Tobacco Tax and Trade Bureau (TTB) requires a sulfite declaration on wine when sulfur dioxide is detected at 10 ppm or more, measured as total sulfur dioxide. The label must read "Contains Sulfites." Wine with less than 10 ppm does not need the statement.

Is there a limit?

TTB guidance says sulfite levels should not exceed 350 ppm total sulfur dioxide. Wine labeled "made with organic grapes" can have added sulfites only up to 100 ppm, and wine labeled "organic" cannot have added sulfites at all. For the differences between these labels, see organic, biodynamic, and natural wine.

Who is sensitive to sulfites?

The labeling rule exists because a small share of people, most often people with asthma, can react to sulfites. Researchers estimate that sulfite sensitivity is uncommon even among people with asthma. This guide covers labeling and winemaking, not medical advice, so anyone with a health concern should talk to a doctor.

Why do buyers of bulk wine care about sulfites?

Total SO₂ tells you a lot about a lot of wine:

• Compliance. The wine has to fit the limits for the label you plan to use.
• Stability. Low levels can mean more risk, and high levels can mean a harsh taste.
• Claims. If you want to make an organic or "made with organic grapes" claim, the numbers and the certification have to support it.

Always ask for lab analysis on the actual lot. See how to buy bulk wine for the full list of numbers to request.

When do winemakers add sulfur dioxide?

Sulfur dioxide is not added once. Many winemakers add small amounts at several points:

• At crush, to reduce unwanted microbes and protect the juice from browning.
• After fermentation and malolactic fermentation, when the wine is most vulnerable to spoilage and oxidation.
• During aging, to replace the SO₂ that gets used up.
• At bottling, so the wine is protected in the bottle.

How much is needed depends on the wine. Wines with a higher pH need more free SO₂ to be equally protected, which is one reason winemakers measure pH and free SO₂ together. Sweeter wines also tend to need more protection because leftover sugar can feed microbes.

How do you read sulfites on a lab report?

A lab analysis of a bulk wine lot usually lists three related numbers:

Ask for the date of the analysis. Free SO₂ falls over time, so a number from months ago may not describe the tank today.

Are sulfites only in wine?

No. Sulfites are used in many foods, including some dried fruits, and food labels also require a sulfite declaration at 10 ppm or more. Wine is one of the few products where sulfites also form naturally during fermentation, which is why nearly every wine contains some.

Find bulk wine by sulfite level

On the bulk wine page, you can filter by maximum total sulfites, along with ABV, vintage, region, and farming practice. To understand where sulfur dioxide fits into the process, read how wine is made.