When the smell of sulfur is detectable in wine, it is considered a fault and can actually become overpowering and irritating to the nose at high concentrations, and points to over-processing with sulfite and/or yeast being stressed during fermentation. It can be easily detected by its distinctive pungent burnt-match smell.
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Possible Causes
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Corrective Actions, if any
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Overuse of sulfite and/or yeast stressed during fermentation.
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- Aerate must/wine by stirring/racking, or
- Treat must/wine with dilute 3% H2O2 solution
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If you detect a sulfur smell in the fermentor, try aerating the wine by successive vigorous rackings. If you detect a sulfur smell in the bottle, aerate the wine by decanting and/or by letting the bottle stand open upright for several hours.
Alternatively, for musts or wines with very high levels of free SO2, up to 100 mg/L, you can treat these effectively with a dilute 3% hydrogen peroxide (H2O2) solution. H2O2 is an effective agent in reducing free SO2. Add the solution at a rate of 18 mL/hL of wine to reduce the free SO2 content by 10 mg/L (free SO2 is actually being oxidized into bound SO2). For example, to reduce free SO2 content by 25 mg/L in a 20-L (5-gal) batch, add 18 × 20/100 × 25/10 = 9 mL of 3% H2O2 solution. Use a syringe to measure the required amount carefully, and run bench trials on a small sample before adding H2O2 to the whole batch. If free SO2 is well beyond 100 mg/L, there might not be any hope to salvage the wine as bound SO2 would become too high to be considered safe.
Warning: The use of hydrogen peroxide (H2O2) requires chemistry laboratory experience and is therefore only recommended for experienced home winemakers. Excessive addition of H2O2 can actually oxidize wine quickly, making it undrinkable.
To prevent sulfur smell, avoid stressing the yeast during fermentation and only add the recommended amount of sulfite based on the wine’s pH to achieve the desired free SO2 level at a molecular SO2 level of 0.8 mg/L. Use the sulfite calculator to determine your sulfite additions.
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