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Common Defects in Wine

Common Defects in Wine. Presented by Jef L. Stebben Stebben Wine Consultants. Stebben Wine Consultants. Formed in 2002 to provide quality winemaking to small producers Consistent focus on quality and improvement at low cost to clients

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Common Defects in Wine

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  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

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