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 Uses: • Define “perceptible” levels for taints or off-flavors in products

• Screen individuals for their sensitivity to key components 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

2. Improperly stored wines

• Surface (flor or film) yeast growing aerobically may oxidize ethanol to acetaldehyde

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) Normal by-product of Saccharomyces growth Influenced by: • Strain • Fermentation temp. • Juice composition VOLATILE ACIDITY (VA)

2. Heterofermentative lactic acid bacteria during primary fermentation VOLATILE ACIDITY (VA)

• Acetyl-phosphate oxidized to produce acetic acid

• Metabolism of citrate by Oenococcus oeni leads to formation of VA

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 mold

2,4,6-trichloroanisole (TCA)

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

S in various forms important: • To yeast in protein biosynthesis, vitamins and coenzymes SULFUR

• From a sensory standpoint

Volatile S compounds with intense and disagreeable odors SULFUR Available as:

2- • Sulfate (SO4 ) 2- • Sulfite (SO3 ) • Amino acids (methionine, cysteine, cystine) SULFATE Yeast need sulfate to support cell growth Once inside cell, sulfate must be reduced to lower oxidation state to be useful to cell

HYDROGEN SULFIDE

• Rotten eggs HYDROGEN SULFIDE Comes from: 1. Yeast (sulfate reduction pathway)

Most important source quantitatively

HYDROGEN SULFIDE

• Integral part of metabolism

• Can prevent its formation if:

 Not stressed  Correct nutrition 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:

H2S + Alcohol Mercaptan

Copper fining possible H5C2-SH

Mercaptan + Mercaptan Disulfide

Copper fining NOT possible H5C2-S-S-C2H5 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 • Leather • Tobacco • Pharmaceutical • Creosote (medicine chest, • Plastic 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- 2-acetyl-1-pyrroline tetrahydropyridine 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!