Wine Defects Workshop - ucanr.edu
Transcript of Wine Defects Workshop - ucanr.edu
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WINE SENSORY DEFECTS
Sue Langstaff
Applied Sensory, LLC
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OUTLINE
Definition of Defect
Thresholds
Origin and description of
wine sensory defects (faults)
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OUTLINE
Examples of aroma defects
Possible treatment
Possible prevention
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The first difficulty that tasters
encounter is to find and to
translate into precise and clear
language the qualities and defects
of a wine...
Pierre Bréjoux
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SENSORY DEFECT
Value judgment
Attribute not wanted
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SENSITIVITY
The degree to which an
observer is responsive to a
stimulus at or near threshold
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THRESHOLD - DEFINITION
A concentration range exists below
which the odor of a substance will
not be detectable under practical
circumstances, and above which
individuals with a normal sense of
smell would readily detect the
presence of the substance
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PROBABILITY FUNCTION
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THRESHOLDS
• Define “perceptible” levels for
taints or off-flavors in products
• Screen individuals for their
sensitivity to key components
Uses:
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AROMA DEFECTS
1. ACETALDEHYDE
2. VOLATILE ACIDITY
(ACETIC ACID, ETHYL ACETATE)
3. CORK TAINT (TCA)
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AROMA DEFECTS
4. SULFUR-DERIVED COMPOUNDS (H2S)
5. ORGANIC SULFUR-CONTAINING
COMPOUNDS (MERCAPTANS)
6. BRETTANOMYCES
7. MOUSEY TAINT
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AROMA DEFECTS
Smells like:
(threshold values
NOT given)
Comes from:
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AROMA DEFECTS
Possible treatment:
Possible prevention:
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AROMA DEFECTS
ACETALDEHYDE
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ACETALDEHYDE
• Over-ripe bruised apples
• Sherry
• Nut-like
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ACETALDEHYDE
Comes from:
1. Wine aging
Chemical oxidation (+O2)
of ethanol
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ACETALDEHYDE
Associated with:
• Increased color depth in
white wines
• Brickish tint in red wines
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“OXIDATION”
“Oxidized” character often
due to high concentration
of acetaldehyde
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ACETALDEHYDE
• Surface (flor or film) yeast
growing aerobically may
oxidize ethanol to acetaldehyde
2. Improperly stored wines
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ACETALDEHYDE
• Growth of oxidative
bacteria on wine surface
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ACETALDEHYDE
Treatment:
• Add SO2 in increments
until free SO2 begins
to decrease
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ACETALDEHYDE
Prevention:
• Inoculate with known cultures
• Control spoilage organisms
• Provide adequate nutrition for organisms
• Monitor critical parameters throughout winemaking process
• Practice good cellar hygiene and sanitation procedures
• Avoid cross contamination of equipment and wine
• Use SO2 appropriately
• Keep containers topped
• Limit oxygen exposure of must/wine
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AROMA DEFECTS
VOLATILE ACIDITY
acetic acid ethyl acetate
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VOLATILE ACIDITY (VA)
• Vinegar (aa)
• Fingernail polish (EtAc)
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VOLATILE ACIDITY (VA)
Comes from:
1. Yeast
Many non-Saccharomyces
strains able to produce
relatively large amounts of
acetic acid and esters
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VOLATILE ACIDITY (VA)
Influenced by:
• Strain
• Fermentation temp.
• Juice composition
Normal by-product of
Saccharomyces growth
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VOLATILE ACIDITY (VA)
2. Heterofermentative
lactic acid bacteria during
primary fermentation
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VOLATILE ACIDITY (VA)
• Metabolism of citrate by
Oenococcus oeni leads
to formation of VA
• Acetyl-phosphate oxidized
to produce acetic acid
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VOLATILE ACIDITY (VA)
3. Acetic acid bacteria (aerobic)
• Acetobacter species of choice
for commercial vinegar (acetic
acid) production
• Also produces ethyl acetate
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VOLATILE ACIDITY (VA)
Post-fermentation sources:
1. Cellar practices
Allowing ullage
(headspace in barrels)
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VOLATILE ACIDITY (VA)
“Acetic aroma” not
exclusively a result of
acetic acid
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VOLATILE ACIDITY (VA)
Acetate esters (ethyl
acetate) contribute
significantly to this defect
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VOLATILE ACIDITY (VA)
Esters:
Volatile compounds
formed by combination of
an alcohol and an acid
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VOLATILE ACIDITY (VA)
ETHYL ALCOHOL + ACETIC ACID ETHYL ACETATE + WATER
CH3CH2-OH + HO-C-CH3 CH3CH2 -O-C-CH3 + H2O
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VOLATILE ACIDITY (VA)
Treatment:
• Acetic acid - reverse osmosis
• Ethyl acetate - difficult to correct
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VOLATILE ACIDITY (VA)
Prevention: • Inoculate with known cultures
• Control spoilage organisms
• Provide adequate nutrition for organisms
• Monitor critical parameters throughout winemaking process
• Practice good cellar hygiene and sanitation procedures
• Avoid cross contamination of equipment and wine
• Use SO2 appropriately
• Keep containers topped
• Limit oxygen exposure of must/wine
• Sterile filter, if necessary or desired
• Store wines in cool, dry area
• Control insects
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AROMA DEFECTS
CORKINESS
AND
CORK TAINT
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CORKED
• Musty
• Moldy
• Dank cellar
• Wet cardboard,
wet newspaper
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CORKED
Comes from:
Phenol (cork) + chlorine
2,4,6-trichloroanisole (TCA)
mold
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CORKED
Chloroanisoles not naturally
occurring in wine
Wine contamination requires
contact or storage with other
contaminated material
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CORKED
TCA most often associated with
corks
Genuine cork taint results from
migration of TCA from
contaminated cork to bottled wine
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CORKED
TCA contamination from other
wood materials:
• contact of wood with chlorine
• mold activity
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CORKED
Other compounds:
• Geosmin (earthy, muddy)
• 2-methylisoborneol (cooked
beets, moldy)
• Guaiacol (smoky, spicy)
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CORKED
Treatment:
• TCA can be removed from
wine with proprietary
methods using plastic
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CORKED
Prevention:
• Screen in-coming corks
(sensory and instrumental)
• Eliminate chlorine from the
winery
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AROMA DEFECTS
SULFUR-DERIVED
COMPOUNDS
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SULFUR
• To yeast in protein
biosynthesis, vitamins
and coenzymes
S in various forms important:
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SULFUR
• From a sensory standpoint
Volatile S compounds with
intense and disagreeable
odors
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SULFUR
• Sulfate (SO42-)
• Sulfite (SO32-)
• Amino acids (methionine,
cysteine, cystine)
Available as:
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SULFATE
Once inside cell, sulfate must
be reduced to lower
oxidation state to be useful
to cell
Yeast need sulfate to
support cell growth
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HYDROGEN SULFIDE
• Rotten eggs
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HYDROGEN SULFIDE
Comes from:
1. Yeast (sulfate
reduction pathway)
Most important source
quantitatively
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HYDROGEN SULFIDE
• Can prevent its formation if:
Not stressed
Correct nutrition
• Integral part of metabolism
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HYDROGEN SULFIDE
2. Elemental sulfur
Fungicide in vineyards
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HYDROGEN SULFIDE
Levels dependent on:
Kind and amount
of elemental sulfur
on grapes
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HYDROGEN SULFIDE
Yeast strains and
physiological condition
during fermentation
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HYDROGEN SULFIDE
Low H2S producers:
Pasteur Champagne,
Epernay 2, Prisse de Mousse
Montrachet produces higher levels
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HYDROGEN SULFIDE
Juice/wine chemistry
• pH
• Utilizable nitrogen levels
• Levels of sulfite and sulfate
• EtOH concentration
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HYDROGEN SULFIDE
Physical parameters • Suspended solids
• Fermentation temp.
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HYDROGEN SULFIDE
Oxidation-reduction
state of must and wine
Environmental factors
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HYDROGEN SULFIDE
H2S can react with alcohol
to form mercaptans
Mercaptans can combine to
form disulfides which can’t be
removed from wine
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“REDUCTION”
“Reduced” character due to
reduced sulfur compounds
such as H2S and mercaptans
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HYDROGEN SULFIDE
Treatment:
• At primary fermentation: H2S + Air
• Copper fining addition with an inactivated
yeast product (generally successful
depending on when performed)
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HYDROGEN SULFIDE
Prevention:
• Inoculate with known cultures
• Control spoilage organisms
• Provide adequate nutrition for organisms
• Limit oxygen exposure of must/wine
• Discontinue use of S-containing vineyard sprays 3
weeks prior to harvest
• Rack new wines off heavy primary lees in first
week fermentation has stopped
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AROMA DEFECTS
ORGANIC
SULFUR-CONTAINING
COMPOUNDS
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THIOETHER OR SULFIDE
-C-S-C-
Sulfur analog of ether
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THIOL OR MERCAPTAN
-C-SH
Sulfur analog of alcohol
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ETHANETHIOL (ethyl mercaptan)
• Onion
• Rubber
• Natural gas
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ETHANETHIOL (ethyl mercaptan)
Treatment:
Mercaptan + Mercaptan Disulfide
Copper fining NOT possible H5C2-S-S-C2H5
H2S + Alcohol Mercaptan
Copper fining possible H5C2-SH
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ETHANETHIOL (ethyl mercaptan)
Mercaptans + Air Disulfides
Aeration NOT a good idea
Disulfides in bottle Mercaptans
Thiols may re-form over time
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ETHANETHIOL (ethyl mercaptan)
Prevention:
• Inoculate with known cultures
• Control spoilage organisms
• Provide adequate nutrition for organisms
• Limit oxygen exposure of must/wine
• Discontinue use of S-containing vineyard sprays 3
weeks prior to harvest
• Rack new wines off heavy primary lees in first
week fermentation has stopped
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AROMA DEFECTS
BRETTANOMYCES/
DEKKERA
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BRETT.
• Barnyard
• Horse (blanket,
sweat, saddle)
• Wet dog
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BRETT.
• Tar
• Tobacco
• Creosote
• Plastic
• Leather
• Pharmaceutical
(medicine chest,
Band-Aid)
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There are people who have been
known to prefer bad wine to
good, just as there are men who
are fascinated by bad women.
André L. Simon
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VOLATILE PHENOLS OF BRETT.
4-ethyl guaiacol (smoky)
4-ethyl phenol (medicinal)
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BRETT.
Comes from:
Spoilage yeast
• Air
• Grapes ?
• Cellar (surfaces, equip.)
• Cooperage (prime source)
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BRETT.
Treatment:
• 4-EP and 4-EG can be
reduced (but not eliminated)
with filtration/adsorption
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BRETT.
Prevention: • Inoculate with known cultures
• Control spoilage organisms
• Provide adequate nutrition for organisms
• Monitor critical parameters throughout winemaking process
• Practice good cellar hygiene and sanitation procedures
• Avoid cross contamination of equipment and wine
• Use SO2 appropriately
• Keep containers topped
• Limit oxygen exposure of must/wine
• Sterile filter, if necessary or desired
• Store wines in cool, dry area
• Control insects
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FLAVOR DEFECTS
MOUSEY TAINT
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MOUSEY TAINT
Aftertaste:
• Mouse urine
• Rancid nuts
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MOUSEY TAINT
Comes from:
1. Brettanomyces (rarely)
2. Lactobacillus (usually)
Produced in presence of
lysine and EtOH
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2-acetyl-3,4,5,6-
tetrahydropyridine
2-acetyl-1-pyrroline
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MOUSEY TAINT
Treatment:
• None known
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MOUSEY TAINT
Prevention: • Inoculate with known cultures
• Control spoilage organisms
• Provide adequate nutrition for organisms
• Monitor critical parameters throughout winemaking process
• Practice good cellar hygiene and sanitation procedures
• Avoid cross contamination of equipment and wine
• Use SO2 appropriately
• Keep containers topped
• Limit oxygen exposure of must/wine
• Sterile filter, if necessary or desired
• Store wines in cool, dry area
• Control insects
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TAKE-HOME POINT
Just because you don’t
smell (or taste) something
“bad” doesn’t mean that the
chemical(s) is (are) not
present in the wine
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TAKE-HOME POINT
The concentration of the
chemicals may be below
your level of sensitivity
OR
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TAKE-HOME POINT
The chemicals have not yet
combined with others to
form off-aromas or flavors
OR
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TAKE-HOME POINT
Everything may be fine!
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It is best to prevent
problems in the first
place than to try and
correct them in the wine!