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Aroma: Yeasty, Sulfury, or Rubbery
A yeasty, sulfury, or rubbery aroma in your finished beer can be attributed to hydrogen sulfide. This substance is normally produced during fermentation in small amounts, but is then carried off by the carbon dioxide that fermentation also produces.
- Noticeable hydrogen sulfide levels are normally caused by a bacterial infection. Higher fermentation temperatures can aggravate the problem.
- Yeast autolysis, where large amounts of dead yeast digest themselves, results in the release of various undesirable substances including bitter resins, lipids, nitrogen, and sulfur-containing molecules like hydrogen sulfide.
- Maintain lower fermentation temperatures so that fermentation runs to completion, yet impact of infection is minimized. Maintain sanitary conditions.
- Minimize transfer of yeast during bottling. Rack beer promptly to ensure that the beer is not left sitting on yeast sediment too long after fermentation is complete. Store beer cool to limit the further activity of yeast in the bottle. Use high-quality yeast in good condition.