Transcript Common Defects in Wine

Common Defects in Wine
Presented by
Jef L. Stebben
Stebben Wine Consultants
Stebben Wine Consultants
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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
Jef L. Stebben
Phone (707) 287-5337
 E-mail [email protected]
 www.stebbenwine.com
(Notes from this presentation will be
posted on the website.)
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Overview
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Reduction in Wine – Sulfides
Oxidation in Wine – Volatile Acidity
Brettanomyces / Dekkera
Sulfides In wine
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H2S – The most common in wine
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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
Mercaptans / Disulfide
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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.
Prevention of Sulfides
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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
Removal of Sulfides
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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
Removal of Disulfides
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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
Samples
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Hydrogen Sulfide
Mercaptan / Disulfide
Volatile Acidity
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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
Sources of Volatile Acidity
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Yeast
Lactic Acid Bacteria
Acetic Acid Bacteria
Conditions that promote
VA
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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
Conditions that promote
VA
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High temperature fermentations
Wines stored with headspace
“Cold Soaking” without SO2
“Cold Soaking” without gassing tank
And many more…
Yeast
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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
Bacteria
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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.
Prevention of VA
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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
Removal of VA
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Mechanical separation of VA from wine
– Reverse osmosis, followed by ion exchange
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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
Samples
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Elevated VA in wine
Oxidation in wine
Brettanomyces/Dekkera
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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)
Brettanomyces/Dekkera
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It can survive on minute amounts of
sugars
It can metabolize cellobiose (from
cooperage)
Thrives in wines with RS and low SO2
Prevention of Brett
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Cleanliness
Maintain SO2 and Topping
Fermentation Management
Control Vectors
– Used cooperage
– Purchased wine
– Pumice and winery waste
Brettanomyces Notes
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SO2 levels over 25 ppm will inhibit
enzymes which allow production of
4EP and 4EG
SO2 will degrade thiamine required for
Brettanomyces growth
Removal of Brett Taint
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Blending of wine is not effective
(sensory threshold for taint is 1.6 ppb)
Mechanical removal
– Reverse Osmosis combined with Ion
Exchange
Samples
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2005 Cabernet Sauvignon
2006 Petite Syrah
References
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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