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