Tips for Limiting Off-Characters during Fermentation
- Choose an appropriate yeast strain: if specific lots of juice are susceptible to off-character formation a yeast trial should be conducted to identify yeast with a reduced tendency to produce the off-note.
- Do not underfeed or overfeed the fermentation: although the exact reason this occurs is unclear, underfeeding has been shown to increase formation of H2S in many strains. Similarly provision of high amounts of nitrogen in combination with aging on the yeast lees can lead to the appearance of sulfur volatiles. In this case the cells have made high concentrations of the S-containing amino acids and their derivatives and these are breaking down during aging.
- Monitor aroma: aroma should be monitored at all stages of production with particular attention paid to the appearance of off-odors that will be difficult to treat if present in the finished wine. Steps should be taken to reduce the formation of the compounds or to encourage their loss due to volatilization.
- Monitor and change production practices: if off-volatiles accompany cold soaks or yeast lees aging, then those practices should be modified to prevent or reduce the appearance of the off-character. Cold soaks and native flora fermentations should be checked daily for the appearance of off-notes. If off-notes arise, the soak should be ended and inoculated immediately, with the same being true for native fermentations. This will limit the need for treatment later on.
- Know your aromas: make sure everyone on the crew is familiar with the aroma of off-characters so that ferments in which they develop can be identified quickly.