Calculate SO2 additions using K-meta or Campden tablets.
Sulfur dioxide (SO2) is the primary preservative in winemaking, preventing oxidation and microbial spoilage. Potassium metabisulfite (K2S2O5) is 57.24% SO2 by weight. One Campden tablet adds approximately 75 mg SO2 per gallon (or 50 ppm per gallon). Target free SO2 levels: white wines 25-40 ppm, red wines 20-35 ppm, sweet wines 40-60 ppm. Higher pH wines need more free SO2 because less is in the protective molecular form. Measure free SO2 before each addition — never add blindly. Legal limits: EU allows 150 ppm total SO2 for red wines, 200 ppm for whites. Organic wines typically stay below 100 ppm. About 1% of the population is truly sulfite-sensitive; the levels in wine (10-200 ppm) are lower than in many processed foods (dried fruit can contain 500+ ppm).