1. Management of Sulfides Formation Linda F. Bisson Department of Viticulture and Enology UCD

2. Management of S-Taints  Diagnosis of Taint  Taint Prevention  Taint Mitigation

3. DIAGNOSIS OF SULFUR TAINTS

4. Correct Diagnosis of Fault Is Important  Is it an S-containing compound?  When did taint first appear?  What factors are associated with appearance of the taint?

5. Is It a sulfur-containing compound?  Be familiar with the characteristic off-odors of sulfur compounds  Other classes of off-odors can be reminiscent of S-compounds  Thresholds of detection are so low compound may be difficult to detect chemically

6. When did taint first appear?  Provides important clues as to the reason taint is occurring  If know why it is being made can take steps to prevent formation

7. What factors are associated with appearance of the taint?  Always found with a specific vineyard?  Associated with unsound fruit?  Associated with specific processing? –Inert gas blanketing –Type of vessel  Associated with specific fermentation conditions?

8. TAINT PREVENTION

9. Preventing S-Taint Formation  Vineyard  Wine chemistry  Yeast strain selection  Fermentation management

10. Preventing S-Taint Formation  Vineyard –Judicious use of elemental sulfur –Eliminate reliance on S-containing pesticides –Address excesses of metal ions –Address vine stress: nutritional or otherwise  Wine chemistry  Yeast strain selection  Fermentation management

11. Preventing S-Taint Formation  Vineyard  Wine chemistry –Minimize use of ‘enabling’ practices »Temperature »Solids content »“Reductive” aging conditions »Role of the ‘lie’ in ‘sur lie’  Yeast strain selection  Fermentation management

12. Preventing S-Taint Formation  Vineyard  Wine chemistry  Yeast strain selection –Match strain to winemaking conditions –Meet the nutritional needs of the specific strain  Fermentation management

13. Preventing S-Taint Formation  Vineyard  Wine chemistry  Yeast strain selection  Fermentation management –Provide adequate nutrition –Keep cells suspended –Mix to prevent reductive stratification of tanks –Remove from lees/yeast residue at first sign of trouble post-fermentation

14. TAINT MITIGATION

15. Elimination of Hydrogen Sulfide Rely on volatility and fermentation gas or inert gas sparging to remove –Need to make sure it is gone and not just converted to a non-volatile form Use of volatiles stripping technologies Precipitation via copper –Emerging issue: health and environmental concerns about copper Use of fining agents Use of strains not producing sulfides

16. Treatments for Higher Sulfides  Removal by reduction of disulfide bond with ascorbate and copper binding  Sulfide trapping by quinones O OH O + RSH OH SR  Removal by charcoal fining

17. Conclusions  Sulfur taints can be controlled  Need to use correct strain  Need to minimize use of compounds in vineyard and winemaking techniques that amplify S-compound formation  Many factors leading to S-taint appearance are still not well understood