Why is sulfur added to wine?

Sulfur has been used in winemaking since antiquity — the Romans burned sulfur wicks inside amphorae to sterilise them. Today, sulfur dioxide (SO₂) is added in various forms: potassium metabisulfite powder, liquid SO₂ solution, or tablets. It is used at multiple stages — on freshly picked grapes, during fermentation to control wild yeast, and at bottling to stabilise the finished wine.

SO₂ works in two complementary ways. As an antioxidant, it binds with oxygen before it can damage the wine's aromas and colour. As an antimicrobial agent, it suppresses acetic bacteria (which turn wine into vinegar) and Brettanomyces yeast (responsible for barnyard and leather off-flavours).

Red wines generally need less SO₂ than whites because their tannins and anthocyanin pigments already provide some antioxidant protection. Sweet wines require more sulfur because residual sugar creates an environment where microbes can thrive.

The sulfur debate has fuelled the rise of "no added sulfite" wines within the natural wine movement. These wines are more fragile and require careful storage — cool, stable temperatures and protection from light. For most consumers, the sulfite levels in conventional wine fall well below any toxicity threshold and pose no health concern. If low-sulfite wines appeal to you, expertvin.be makes it easy to filter for organic and natural options.