Common Defects in Wine

1. Common Defects in Wine Presented by Jef L. Stebben Stebben Wine Consultants

2. Stebben Wine Consultants • Formed in 2002 to provide quality winemaking to small producers • Consistent focus on quality and improvement at low cost to clients • Now working with wineries from 9,000 cases to home winemakers

3. Jef L. Stebben • Phone (707) 287-5337 • E-mail jef@stebbenwine.com • www.stebbenwine.com (Notes from this presentation will be posted on the website.)

4. Overview • Reduction in Wine – Sulfides • Oxidation in Wine – Volatile Acidity • Brettanomyces / Dekkera

5. Sulfides In wine • H2S – The most common in wine • Can form during fermentation • Forms in stressed fermentations • Low nitrogen musts • Utilizes vineyard Sulfur (Residue on skins) • Low levels of Vitamins in musts • High levels of Cysteine • Yeast strain • Too much SO2

6. Mercaptans / Disulfide • Mercaptans are stable molecules forming from large amounts of H2S and Ethanol and/or reduction of Amino Acids during storage. • Dimethyl Disulfide and Diethyl Disulfide can form from mercaptans and need to be reduced before they will can be removed from wine.

7. Prevention of Sulfides • Vineyard Practices – No Sulfur post veraison • Harvest sound balanced fruit • Add VITAMINS to fermentations • Add NUTRIENTS to fermentations • Do not add Cu prior to fermentation • Rack whites after settling • Do not ferment in the presence of Bentonite

8. Removal of Sulfides • H2S can be removed by contact with Copper. (CuSO4 or other method) • Often the addition of nutrients during fermentation will remove H2S • Often racking or splashing the fermentation will remove H2S

9. Removal of Disulfides • Perform a test to determine the presence of Disulfides (Cd++, Cu++, and Ascorbic Acid) • Use SO2 to reduce Disulfides to Mercaptans • Treat with CuSO4 to remove H2S and Mercaptans

10. Samples • Hydrogen Sulfide • Mercaptan / Disulfide

11. Volatile Acidity • Defined as those acids which may be removed from solution by steam distillation • Generally taken to mean Acetic Acid • May include Carbonic, Sulfurous, Sorbic, Lactic, Formic, Butyric, and Propionic Acids

12. Sources of Volatile Acidity • Yeast • Lactic Acid Bacteria • Acetic Acid Bacteria

13. Conditions that promote VA • Wines with residual sugar • Wines made from Botrytis infected fruit • Wines with Brettanomyces • Stuck Fermentations • ML fermentation in the presence of sugar • High sugar fermentations

14. Conditions that promote VA • High temperature fermentations • Wines stored with headspace • “Cold Soaking” without SO2 • “Cold Soaking” without gassing tank • And many more…

15. Yeast • Kloeckara apiculata / Hanseniaspora uvarum will produce large amounts of Ethyl Acetate • Brettanomyces will produce acetic acid • Sacharomyces will produce VA in a normal fermentation (about 0.4 g/L) • VA production is higher in the presence of Botrytis cineria

16. Bacteria • Lactic Acid Bacteria will utilize sugars during fermentation to make VA. They can out-compete yeast and stop a fermentation. • Acetic Acid Bacteria can utilize sugars and oxidize ethanol to make VA. They are more common after fermentation.

17. Prevention of VA • Cleanliness and good cellar technique • Good, clean, and sound fruit • Keep up with topping in barrels • Overflow barrels when topping, combined with direct addition of SO2 • Minimize headspace in tanks • Keep up with monthly SO2 additions

18. Removal of VA • Mechanical separation of VA from wine • Reverse osmosis, followed by ion exchange • Blending • Re-fermentation of contaminated wine is not very effective and may spread the contamination • Tannin and/or Yeast lees may reduce perception of oxidation in wine

19. Samples • Elevated VA in wine • Oxidation in wine

20. Brettanomyces/Dekkera • One of the most common spoilage yeasts • Present in every wine region • It has never been isolated in the vineyard • Contributes unwanted phenols in wine • 4-ethylguaiacol (4EG) • 4-ethylphenol (4EP)

21. Brettanomyces/Dekkera • It can survive on minute amounts of sugars • It can metabolize cellobiose (from cooperage) • Thrives in wines with RS and low SO2

22. Prevention of Brett • Cleanliness • Maintain SO2 and Topping • Fermentation Management • Control Vectors • Used cooperage • Purchased wine • Pumice and winery waste

23. Brettanomyces Notes • SO2 levels over 25 ppm will inhibit enzymes which allow production of 4EP and 4EG • SO2 will degrade thiamine required for Brettanomyces growth

24. Removal of Brett Taint • Blending of wine is not effective (sensory threshold for taint is 1.6 ppb) • Mechanical removal • Reverse Osmosis combined with Ion Exchange

25. Samples • 2005 Cabernet Sauvignon • 2006 Petite Syrah

26. References • Concepts in Wine Technology, Yair Margalit, PhD., The Wine Appreciation Guild,2004 • Production Wine Analysis, Bruce Zoecklein, Kenneth C. Fugelsang, Barry H. Gump, & Fred S. Nury, Van Nostrand Reinhold, 1990 • Wine Analysis and Production, Bruce Zoecklein, Kenneth C. Fugelsang, Barry H. Gump, & Fred S. Nury, Aspen Publishers, 1999 • Wine Microbiology, Kenneth C. Fugelsang, Chapman and Hall, 1997