Problematic Fermentations

Problematic fermentations are ones that deviate from the desired results a winemaker is looking to achieve. The characteristics a winemaker looks for in a quality fermentation are: a vigorous fermentation that finishes in an acceptable time period, completion to dryness, no production of off flavors or spoilage, some tolerance to typical processing events like temperature shifts and increasing ethanol, and a yeast that flocculates so it can be removed from the finished wine. Occasionally not all of these occur. The fermentation is considered problematic when this happens. The biggest concern for winemakers is usually a fermentation that progresses slowly or stops before resulting in dry wine. Large amounts of time, extra space, and extra processing are often required to remedy the problem to prevent spoilage. Common issues causing problematic fermentation include:

• Nitrogen deficiency in the juice. This can be prevented by the addition of yeast nutrients prior to fermentation. If nitrogen deficiency is suspected during fermentation then an addition of DAP is recommended.
• Lack of sufficient oxygen while the yeast is developing can also lead to problems, as yeast use oxygen during the reactions performed to stabilize their membranes for high stress environments like wine.
• Aggressive stress during fermentation, such as extreme temperatures, can also cause problems.

Fermentations should be constantly monitored for their progress, and if any problems do develop, immediate action should be taken. Treatment with sulfur dioxide is recommended followed by further assessment of the problem’s cause if any spoilage is a concern. The best defense against problematic fermentations is ensuring healthy yeast is growing in your wine.