Determine the active antimicrobial SO2 in wine based on pH and temperature.
Wine Analysis
ppm (mg/L)
Protection Level
Enter wine analysis to see protection level
Overview
In winemaking, sulfur dioxide (SO2) exists in various forms. 'Molecular' SO2 is the only form that actually inhibits bacteria and spoilage yeast. Its effectiveness depends heavily on the wine's acidity (pH).
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Pro Tips
Target 0.8 mg/L molecular SO2 for white wines and 0.5 mg/L for reds for shelf stability.
If your pH is above 3.6, you'll need significantly more Free SO2 to achieve the same protection.
Measure your Free SO2 before and after bottling; it drops as it reacts with oxygen.
Temperature affects the pKa of SO2; warmer wine requires slightly more Free SO2 for the same molecular level.
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Fun Facts
"SO2 is a byproduct of yeast fermentation; even if you don't add sulfites, wine will contain some."
"The 'No Sulfites Added' label means less than 10 ppm total SO2."
"Red wines require less SO2 than white wines because tannins provide natural protection."
"Most commercial wines contain 20–150 ppm total SO2; the legal limit in the US is 350 ppm."
