Sulfur-containing volatile compounds are perhaps the most challenging of the off-aromas that can form during fermentation. These compounds are reactive and can exist in different chemical states making both detection and removal difficult. The off-aroma may seem to have disappeared only to return later in processing as chemical conditions change. More oxidized forms may be non-volatile or non-aromatic, but if the environment becomes more reduced will be restored to the aromatic reduced form and reappear as a sensory defect.
The first thing to try with an arrested fermentation is to expose the culture to air. If survival factors are limiting this is often enough to encourage the yeast to finish the fermentation.
