What Are Sulfites in Wine

Sulfites in wine often spark questions and concerns, leaving many people wondering what they really are and what role they play in the winemaking process. Are they natural? Do they cause headaches? And what makes "no-added sulfite" wine different? 

In this blog, we’ll take a deeper look into why sulfites naturally occur in wine, clear up some of the most common myths about their effects on the body and how some winemakers are crafting wines without added sulfites.

What are sulfites?

The lowdown: Sulfites are sulfur-based compounds that occur naturally during food and beverage production, including winemaking, as a byproduct of yeast and bacteria activity. They’re also added in small amounts during the winemaking process to preserve freshness and protect the wine from spoilage and oxidation. 

Sulfites occur naturally in wine and other foods as a byproduct of fermentation.

• Sulfates are a naturally occurring type of salt found in soil, water and plants.
• Microorganisms can transform sulfates into sulfites during fermentation and aging.
• During fermentation, microorganisms break down amino acids, leading to the release of sulfur-containing compounds such as sulfur dioxide and sulfites.
• Yeast and bacteria produce enzymes that convert sulfur compounds into sulfites during metabolism.

Sulfites in wine

During fermentation, the activity of yeast and bacteria produce sulfites.

• Yeast (typically species of Saccharomyces cerevisiae) converts sugars in grape juice into alcohol and carbon dioxide and also produces small amounts of sulfur dioxide (SO₂) as a byproduct.
• After the primary alcoholic fermentation, some winemakers choose to initiate malolactic fermentation – a process where lactic acid bacteria convert tart malic acid into softer lactic acid to add smoothness to the final product.

Natural sulfites act as a preservative and prevent spoilage by controlling oxidation.

• Sulfites inhibit microbial activity that could impact the wine’s taste or spoil it entirely.
• Sulfites help neutralize oxygen molecules and protect the wine’s delicate components like color, flavor and aroma.
• Sulfites assist in keeping the wine visually appealing, preventing haze or sediment from developing after bottling.

Added sulfites also serve a purpose too, allowing winemakers to preserve their product, control fermentation and stabilize the wine.

• Sulfites are added to protect the wine from bacteria and wild yeast that could spoil the wine or interfere with the fermentation process.
• By suppressing wild yeast and bacteria, sulfites allow winemakers to introduce specific strains of yeast for a more controlled and predictable fermentation.
• Sulfites help stabilize the wine after fermentation by preventing oxidation and microbial spoilage.

To ensure transparency, wines that contain 10 ppm or more of sulfites must include a warning label that states “Contains Sulfites.” 

• This applies to wines sold in the United States and many other countries.
• Wines with added sulfites might contain up to 300 ppm, depending on the type of wine.
• For example, white and sweet wines often contain more sulfites than red wines because they are more prone to oxidation and microbial activity.

Misconceptions about sulfites in wine

What to know: Sulfites in wine are often misunderstood, leading to myths that can steer wine lovers down the wrong path. 

One of the most widespread myths about sulfites is that they cause headaches after drinking wine. 

• While some people are sensitive to sulfites and may experience allergic reactions, the majority of wine-related headaches are caused by other factors, such as histamines (especially common in red wines) and the alcohol content itself.
• Sulfite allergies are rare and most common in people with asthma.
• An allergic reaction to sulfites typically includes respiratory issues such as wheezing, shortness of breath or nasal congestion, rather than headaches.

Another misconception is that organic or natural wines are entirely sulfite-free.

• While these wines may have fewer added sulfites, they still contain naturally occurring sulfites and might even have small amounts added for stabilization.

Histamines in wine

At a glance: Histamines are organic compounds found naturally in your body and various foods, including wine. When it comes to wine, histamines can sometimes be linked to adverse reactions, particularly headaches or allergy-like symptoms. 

Histamines belong to a group of compounds called biogenic amines. 

• They are produced by the body as part of its immune response and are also formed in foods and beverages during fermentation.
• Histamines are found in a variety of items, from aged cheese and cured meats to beer and wine.

During winemaking, histamines form when certain bacteria convert amino acids in grape skins into biogenic amines, including histamine. 

• Red wines tend to have higher histamine levels than white wines because they are fermented with their skins for extended periods, extracting more histamine-rich compounds.
• White wines, on the other hand, are typically fermented without the skins, resulting in lower histamine content.
• Wines aged in barrels or for extended periods often have higher levels of histamines due to the activity of bacteria during maturation.

Headaches are often linked to histamines, especially when drinking wine.

• However, other factors like tannins and alcohol content also play a role.
• Histamines can dilate blood vessels, potentially causing flushing of the skin or nasal congestion after drinking wine.
• Additionally, dehydration caused by alcohol and individual sensitivity to alcohol play a role.

Sulfite-free wine

Diving deeper: The term “sulfite-free wine” is misleading because even if sulfites aren’t added, they still occur naturally. Instead, “no added sulfites” is a more accurate description. In any case, these wines can spoil quickly and have a shorter shelf life.

Sulfite-free wine refers to wine that is made without any added sulfites. 

• Legally, wines labeled as sulfite-free must contain less than 10 parts per million (ppm) of total sulfites.
• While these wines don’t have any sulfites added during the winemaking process, they still contain naturally occurring sulfites.
• As a result, they can actually have higher sulfite levels than wines labeled as sulfite-free, depending on the yeast activity and fermentation conditions.

Producing sulfite-free wine is a delicate and labor-intensive process because alternative strategies are needed to ensure quality and stability. 

• The process starts with using high-quality grapes, free of disease or damage, so unwanted bacteria isn’t introduced.
• The equipment, barrels and fermentation vessels must be meticulously cleaned and sanitized to avoid contamination by unwanted microbes.
• Careful temperature management is essential in preventing spoilage during fermentation and storage.
• Advanced filtration systems help remove any remaining yeast, bacteria or other particles that could cause spoilage after fermentation.
• Limiting exposure to oxygen during production and bottling via nitrogen or argon protects against oxidation.

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