What is the role of sulfur in wine production?

Synthetic sulfites added to wine are used as an antioxidant preservative and stabilizer. Sulfur started to be used in winemaking in the early 1900s to stop bacteria and other yeasts from growing. It’s used to prevent micro organisms and oxidation from spoiling wine. Sulfur dioxide (SO2) is a natural by-product of fermentation so there will almost always be trace amounts of naturally occurring sulfites in any wine.

Sulfite Regulations

  • Under the USDA National Organic Program, wines labeled as Organic Wine can have no added sulfites. Only those wines can display the USDA Organic Seal.
    • Sulfite limits in wine by category:
    • Organic Wine: Under 10 ppm naturally occurring sulfites
    • “Made with Organic Grapes” and Biodynamic wine: Up to 100 ppm added sulfites
    • Conventional wine: Up to 350 ppm added sulfites

Why is it difficult to produce No Sulfites Added Wine?

  • Because sulfur is not used to prevent bacteria during production and storage, producing NSA wines requires great care at every step.
  • Grapes are hand-picked, often at night to avoid exposure to the sun and potential bacteria.
  • Only the most pristine grapes can be used in production of the wine. Grapes are sorted and those with blemishes are taken out of production.
  • Indigenous wild yeasts which do not form SO2 are used in production.
  • Strict hygienic conditions must exist throughout the production process. Avoiding all contact with oxygen is imperative to avoid spoilage.
  • The wines are produced and fermented in steel tanks. There are no barrel-aged NSA wines.
  • Care must be taken in the bottling process to ensure a clean, bacteria-free environment and avoid any exposure to oxygen. A nitrogen flush is added to the wine right before placing the cap or cork.
  • Stelvin screw caps or alternative corks (such as those produced with natural sugar cane biopolymers) are used as they form a tighter seal and can keep out oxygen for a longer time than cork. They preserve the aromatic freshness of the wine and allow it to age properly on the shelf.
  • Under normal, proper handling conditions, No Sulfites Added organic wines from Europe arrive stateside in great condition and have a shelf life similar to wines with added sulfites.

Why is it difficult to make a No Sulfites Added White Wine?

  • Wines with higher sugar content tend to need added sulfur to prevent secondary fermentation of the remaining sugar.
  • Red wine grapes contain additional natural preservatives-such as tannins from the grape skins-so is more stable. Red wine tannins contain high levels of polyphenols, which act as natural antioxidants.
  • Because the white organic wines are less stable, importing and handling requires extra care and their shelf-life is limited.