Wine Faults: Symptoms and Causes
Definition of terms for wine faults, as set out by the INAO in AOC certification



Organoleptic tests - these description terms are used by the INAO when deciding whether to grant AOC certification for wines.

These faults have different levels of severity, and their presence does not necessarily mean a wine will not receive its AOC - this will depend on quantity and intensity (marked as weak, medium and strong), and will be be subject to either a simple warning or sanctions

Words expressing something negative in a wine (national usage)
Taste: smell of acetate d'ethyle (ethyl acetate, glue)
Cause: Acetic acid bacterial spoilage, et/or certain yeasts. Oxidation of alcohol by acetic acid bacteria that has turned into an esther (acetate d'ethyl)
Molecule: acetate d'ethyle / ethyl acetate

Taste: taste and smell of acetic acid (vinegar)
Cause: alteration of the wine from acetic bacteria, from lactic bacteria or yeasts
Molecule: acide acétique / acetic acid
Opposite fault: n/a

Taste: sensation of aggression in the moth coming from a low pH
Cause: inbalance of the composition of the wine that is highlighting the organic acids within it
Molecule: tartaric acid, malic acid, citric acid
Opposite fault: heavy, flat

Sweet-sour (aigre-doux)
Taste: smell/flavour of sourness (aigre) and a sweet taste
Cause: acetic bacteria
Molecule: acetic acid and sugars
Opposite fault: n/a

Alcooleux / overly high in alcohol
Taste: impression of heat
Cause: predominance of alcohol
Molecule: alcohol, specifically ethanol
Opposite fault: n/a 

Alliacé (onion)
Taste: smell and taste of onion or garlic
Cause: usually this is a problem of reduction or contamination of the harvest
Molecule: certain sulphorous molecules
Opposite fault: n/a

Bitter almond
Taste: taste of bitter almonds
Cause: formation of benzoique aldehyde from benzylic alcohol sometimes found in lining of vats lined with expoxy-resin
Molecule: benzoic aldehyde (benzaldehyde)
Opposite fault: n/a


Taste: sensation of bitterness
Cause: this can be a spoilage indication of glycerol breaking down to form acroleine. The combination of this and the polyphenols such as wine tannins give many substances a bitter taste, also found in wine made from unripe grapes, or that have had too much tannic suspbstances extracted from them. An excess of tannins can also cause bitterness.

Molecule: acroléine (acrolein, a unsaturated aldehyde), polyphenols.
Opposite fault: syrupy

Apre (strong astringency)
Taste: a strong and disagreeable feeling of astringency
Cause: imbalance of tannins in certain red wines reinforced by acidity
Molecule: polyphenols
Opposite fault: syrupy

Drying /assechant
Taste: lack of balance, lacking in roundness, leaving an impression of dryness in the mouth
Cause: imbalance of flavours and/or acidity, overly high volatile acidity, excess of SO2
Molecule: polyphenols, SO2, acetic acid
Opposite fault: syrupy

Taste: constriction of tissues in the mouth
Cause: imbalance of tannins
Molecule: polyphenols
Opposite fault: syrupy

Rot (botrytis, pourriture grise)
Taste: Dusty, earthy or rotten flavours
Cause: the grey rot parasite botrytis cinerea on the grapes at harvest time, development of the mushroom of rot on the grapes, invariably from rain either during veraison (colour change) or the ripening period
Molecule: geosmin
Opposite fault: n/a

Corked (bouchonné)
Taste: taste and smell or wet/musty cork
Cause: contamination of the cork (or other material) by TCA
Molecule: chloroanisols, TCA
Opposite fault: n/a

Browning / brunissement
Taste: red wine goes brown, white wine goes rusty yellow
Cause: premature oxidation either chemical or from enzymes due to the presence of laccase. The polyphenols are oxidised into quinones and polymerise, so causing colour change to brown/rust
Molecule: quinones
Opposite fault: n/a

Butyric / Butyrique
Taste: taste and smell of butyric acid (rancid butter)
Cause: bacterial spoilage
Molecule: acide butyrique
Opposite fault: n/a

Rubber / Caoutchouc
Taste: smell and taste of burnt rubber, or rubber
Cause: diverse, bad treatment of the harvest, bad evolution of the wine
Molecule: benzothiazole
Opposite fault: n/a

Taste: abnormal colour, limpidity and/or deposits
Cause: chemic or enzyme alteration
Opposite fault:

Mushroom / Champignon
Taste: smell and taste of mushrooms
Cause: moissisures (molds)
Molecule: octène-3-ol, chloroanisol, acétate de méthionyle
Opposite fault:

Taste: cooked character
Cause: oxidative ageing, overripe grapes
Opposite fault:

Ciment / cement
Taste: taste of dry, dusty cement
Cause: generally this comes from a badly maintained cement tank
Opposite fault:

Altered colour
Taste: prematurely evolved colour, losing its original (intended) hue and aspect
Cause: premature oxidation (chemical or enzymatic) due to presence of polyphenoloxydases (laccase). The polyphenols are oxidised into quinones and polymerise, so causing colour change to brown/rust
Molecule: quinones
Opposite fault:

Taste: specific odour of creosote
Cause: possibly comes from the stakes used to hold up the vines in the vineyard, the trellising support, which may have been treated with creosote.
Opposite fault:

Creux / hollow
Taste: An absence of taste sensations and density, notably in the mid palate
Cause: lack of structure, possibly from overly high yielding vines
Opposite fault: heavy

Croupi / stagnant
Taste: smell of drain water, or stagnant water (odeur de serpilliere ou d'eau croupi)
Cause: wine stored in unclean vats/containers, or on lees that have an infection/are unclean
Molecule: Sulphurous components
Opposite fault: oxidised

Taste: specific copper taste, almost always reinforced by a strong bitterness
Cause: badly-maintained winery materials (copper taps), or mercaptans formed from copper
Molecule: copper salts
Opposite fault: H2S

Discoloured / Decoloré
Taste: Colour has lost its intensity
Cause: diverse -infection, treatment, too much SO2 etc
Opposite fault: (taché in white wine)

Taste: lacknof balance between sweetness and acidity in whites, between sweetness-acidity-astringency in reds
Cause: lack of ripeness in grapes, overly high yields, incorrect vinification
Opposite fault:

Diluted / Dilué
Taste: lacks concentration
Cause: overly high yields, rain at harvest / end of season, issue with winemaking
Molecule: H2O/water
Opposite fault: heavy, syrupy

Overly sweet
Taste: sweetness over all other tastes
Molecule: sugars
Opposite fault: acid, drying, astringent, sour

Barnyard / Ecurie / Phenolé
Taste: strong smell of stables, barnyard, horse sweat (red wines)
Cause: yeasts from the Brettanomyces strain, due to lack of hygiene and not enough sulphiting
Molecule: ethyl-4-phenol and ethyl-4-gaiacol
Opposite fault:

Eventé (oxidised)
Taste: Ethanal taste (pomme blette, browning apples)
Cause: ethanol is oxidised and forms ethanal (either due to presence of catalysts such as copper or iron) or because of specific mycodermic yeasts or acetic acid bacteria, or wine has an excess of free ethanal without enough free sulphur (SO2 libre) to protect it
Molecule: ethanal (acetaldehyde)
Opposite fault: reduced

Filant /oily
Taste: looks viscous and oily
Cause: maladie de la grasse/oily sickness from formation of polysaccharides from lactic bacteria
Molecule: polysaccharides
Opposite fault:

Taste: specific aroma from grapes of the vitis labrusca grapes and their hybrids
Cause: Amercian vine species vitis labrusca (or occasionally extreme hydric stress in vines)
Molecule: anthranilate de méthyle
Opposite fault:

Taste: tactile sensation of small prickles/bubbles in the mouth
Cause: alcoholic or malolactic fermenation
Molecule: carbon dioxide (dioxyde de carbone, CO2)
Opposite fault:

Taste: specific smell of geraniums
Cause: sorbic acid broken down by lactic bacteria
Molecule: 2-ethoxyhexa-3.5 diene
Opposite fault:

Gouache (poster paint)
Taste: fresh paint, or pharmaceutical smells
Cause: bacterial infection, infection of certain vinification yeasts
Molecule: vinyl-4-phenol and vinyl-4-gaiacol
Opposite fault:

Goudron (tar)
Taste: smell of warm tar (used for lining roads)
Cause: various contaminations
Opposite fault:

Grêle / Hail
Taste: smell and taste dominated by herbaceous/vegetal characteristics, and sometimes moisie (musty)
Cause: hail affecting the grapes, damaging them, compromising their health state and leading to unripe grapes (usually because they had to be harvested quickly)
Opposite fault:

Grossier / fat
Taste: lack of finesse and elegance
Cause: raisins lacking in balance, badly managed vinification
Opposite fault:

H2S /rotten eggs
Taste: rotten eggs, or highly reduced wine
Cause: diverse; residue of sulphur used on the grape skins, insufficient clarification of white must before fermentation, insufficient aeration during vi ification and ageing, insufficient racking.
Molecule: h2S

Opposite fault: oxidised

Taste: leafy taste / crushed herbs
Cause: lack of maturity, unripe grapes, leafs in the harvest, badly handled grapes at harvest
Molecule: cis-3-hexanol
Opposite fault:

Hydrocarbons / petrol

Taste: smell of petrol and its derivatives
Cause: contamination of the grapes by some external factor, sometimes aromatic evolution during ageing
Molecule: trimethyl-dihydronaphtalene
Opposite fault:

Iodé / Iodized

Taste: smell of iodine
Cause: generally strong problem with rot at harvest (or external contaminant)
Opposite fault:

Taste: smells and tastes like milk /dairy products
Cause: badly controlled fermentations, transformation of sugar by lactic bacteria (usually lactobacillus heterofermentary)
Molecule: exess of lactic acid
Opposite fault:

Taste: yeasty smell or taste
Opposite fault: oxidised

Taste: smell of reduced lees
Cause: often wine left on lees too long or badly-maintained (often leading to reduction)

Opposite fault: oxidised

Heavy / Lourd
Taste: unbalanced, usually due to low acidity
Cause: overripe grapes at harvest
Opposite fault: acid, thin

Thin / Maigre
Taste: lack of body and matière
Cause: underripe grapes at harvest
Opposite fault: heavy

Bad oak / mauvais boisé
Taste: taste of oak barrels that are either too old or badly maintained
Cause: bad upkeep in cellar
Opposite fault:

Bad taste
Taste: something unpleasant other than other things listed here
Cause: unknown
Opposite fault:

Bad smell
Taste: something unpleasant other than other things listed here
Cause: unknown
Opposite fault:

Taste: fetid smell, reminiscent of town gas (there can of course be good mercaptans, it they are also known as thiols and are classic aromatic markers of sauvignon blanc), but here we are in the bad sense of the word)
Cause: reduction, H2S, residue of sulphur-containing compounds on grapes, insufficient aeration during vinification or ageing, not enough racking
Molecule: R-SH, methanethiol, ethanethiol
Opposite fault: oxidised

Nb Useful look at mercaptans in wine here:

Taste: hard, metallic taste
Cause: indetermined (external contaminant?)
Opposite fault:

Moisi / Moldy
Taste: taste of molds /rot
Cause: eirher rotten grapes at harvest or wine stored in badly- maintained container (often wood), or TCA in cellars
Opposite fault:

Mou (too soft, flabby)
Taste: lack of acidity so unbalanced, lacks definition
Cause: excessive de-acidification, or problem in original grape
Opposite fault: acidic

Taste: visual, aromatic and taste markers of oxidation (curry, pomme blette, darkened colour)
Cause: exposure of wine to air, insufficient SO2 etc leading to formation of ethanal and other molecules
Molecule: sotolon, ethanal, o-aminoacetophenone
Opposite fault:

Taste: paper-taste
Cause: usually bad use of a plaque filter
Opposite fault:

Not clean / pas net
Taste: unclean taste or smells
Cause: various, undetermined
Opposite fault:

Taste: medical aroma
Cause: (similar to paint smell)
Molecule: vinyl-4-phenol and vinyl-4-gaiacol
Opposite fault:

Pheniqué (made from rotten grapes)
Taste: extreme rotten grapes, putrid smell
Cause: extreme rot at harvest
Opposite fault: H2S, reduced

Taste: smell of styrene plastic
Cause: usually fault with glass-fibre vats
Molecule: styrene
Opposite fault:

Flat / Plat
Taste: lacking in odours and tastes
Cause: either original grapes or wine breaking down
Opposite fault: acid

Plombé / leaden
Taste: greying colour in white wine
Cause: unintended oxidative development
Opposite fault:

Poivron /green pepper
Taste: specific taste and smell of fresh green pepper aroma
Cause: lack of ripeness in certain varieties (and a marker for sauvignon blanc, so not a fault unless extreme)
Molecule: IBMP - methoxypyrazine
Opposite fault:

Taste: specific and highly unpleasant bad pungent smell
Cause: often solvent in epoxy-resin-lined tanks
Molecule: aldehyde benzoique
Opposite fault:

Taste: decomposing organic matter, often in reductive environment
Cause: usually rotting lees
Molecule: sulphur-bearing compounds, mercaptans
Opposite fault: oxidised

Taste: taste of stalks (vegetal aroma, hard tannins, herbaceous)
Cause: excessive maceration of the stalks
Molecule: polyphenols, herbaceous volatile aromas
Opposite fault:

Rancid butter
Taste: taste and smell of rancid butter
Cause: oxidation of fatty components
Opposite fault:

Reduced / Reduit
Taste: H2S
Cause: wine in state of reduction, insufficiently aerated
Molecule: H2S, sulphur-bearing compounds
Opposite fault:

Taste: pine resin smell
Cause: premature evolution
Opposite fault:

Soapy / Savonneux
Taste: taste more or less intense of soap (often used w young eaux-de-vies)
Cause: excessive fatty acids and their esthers
Molecule: caproate and caprate d'ethyle
Opposite fault:

Taste: impression of dryness in mouth
Cause: bad quality tannins, excessive SO2, volatile acidity, excessive filtration
Opposite fault:

Taste: syrupy sensation
Cause: unbalanced sugar/acidity
Molecule: sugars, polyphenols
Opposite fault: thin etc

Sulphur (SO2)
Taste: a sensation as well as a smell (somesethique), burns and dries
Cause: excess sulphur dioxide in form of free SO2
Molecule: SO2
Opposite fault: oxidised

Taste: taste of solvant
Cause: aromatic inbalance, external contamination
Molecule: esters, superior alcohols
Opposite fault:

Mousey /Souris

Taste: Specific spoilage that is known as mousey (usually develops slowly in the mouth and is very persistent)
Cause: badly stored wines, insufficient sulphur dioxide, Brett yeasts, lactic bacteria (lactobacilles)
Molecule: aveto-tetrahydropyridine
Opposite fault:

Taste: red hints in white wine
Cause: bad extraction of white juice from red grapes (or contamination of white wine by red juice)
Molecule: anthcyanes
Opposite fault:

Tartre sec / tartar/ potassium salts
Taste: dusty taste reminiscent if potassium bitartrate
Cause: deposits of tartar / potassium salts /mineral in old vats
Opposite fault:

Terreux / Earthy
Taste: tastes of earth, soil, smell similar to TCA but often a little less musty, more earthy
Cause: certain rot at harvest (or not fully cleaning grapes if in contact with earth), underripe grapes with some botrytis
Molecule: Geosmin
Opposite fault:

Usé (oxidised)

Taste: premature oxidation
Cause: badly stored
Molecule: ethanal
Opposite fault:

Negative words (local useage, Bordeaux/sw France, as defined by INAO)

Taste: banana, bonbon anglaise
Cause: formation of the ester from isoamyle alcohol (methyle-3-butanol-1) often brought about by certain alcoholic fermentation conditions or carbonic maceration (absence of oxygen, low temperature vinification, highly clarified must, certain yeast strains)
Opposite fault:

Taste: olfactive sensation of musk, venison, leather
Cause: wine is slightly reduced (but reversible) or organoleptic character of certain wines
Opposite fault:

Taste: no aromatic or flavour expression
Cause: generally due to wine in a reductive environment, or wine not conduicive to tasting (too young perhaps, needs to open with exposure to air)
Molecule: n/a
Opposite fault: oxidised

Taste: tannins are predominant over all other elements
Cause: insufficient ripeness at harvest, or too much extraction of tannins
Molecule: polyphenols
Opposite fault: syrupy

Trouble / Cloudy
Taste: Elements in suspension in the wine
Cause: insufficient preparation of the sample
Molecule: n/a
Opposite fault: n/a

Tuilé / brick/tile
Taste: presence of abnormal orange tints
Cause: oxidation
Molecule: aldehydes
Opposite (not fault): primeur red wine

Words that express negative expressions of typicity (as defined by INAO for AOC Agrément)

Taste: colour, aromas and/or tastes not achieving minimum quality levels typical for the AOC
Cause: diverse
Molecule: n/a
Opposite fault: n/a

Lack of typicity
Taste: not corresponding to the organoleptic requirements of the AOC
Cause: either using grapes from outside the AOC, or poor quality original grapes, or incorrect oenological practices, or some spoilage of the wine
Molecule: n/a
Opposite fault: n/a

Without character
Taste: neutral of odours and tastes
Cause: either insufficent composition of original grapes, or spoiling of the wine
Molecule: n/a
Opposite fault: n/a