Defects in wine… Really ?

I might be lying ? The wine would have defects… But is it really possible ? The drink of Dionysus, no, no ! It can not be that perfect !

Hello, Earthlings, you will go back to earth ! Unfortunately, the wine has defects… You probably know the most famous among them which is your obsession… You have cold sweat when you buy a bottle because you fear that it will taste a ‘delicious’ corked taste ! But this is not the only defect you may find in your bottle. Indeed, sometimes the wine is not only given you its secrets but it is also poisoned with a small gift (even if these defects are not dangerous to health) !

I know many of you know these defects but I’m still tempted to redo the list and explain the origins ! I did not have bad surprises recently but it’s true that it happened to me ! Then zoom on wine defects… Which only makes this God drink more human !

Wine defects are numerous… And yes ! They have several olfactory consequences : they mask the flavors, they cause a loss of pleasure, they alter the perception and they manage to release a product.

It’s possible to classify wine defects in order to explain them. No wine is immune : indeed, it’s sometimes the fault of the winemaker, but from time to time, we can’t blame the winemaker because it’s not the culprit!

1) Defects due to immaturity 

You guessed it, the grape is supposed to be harvested at full maturity. But sometimes this is not the case : a lack of ripeness can give wines a plants, grassy taste.

– HEXANAL (or HEXENAL): it gives taste of grass or grass clippings (grass like fescue or bluegrass). This molecule, therefore it’s very important, is considered as a defect. Some varieties such as Vinho Verde or Müller-Thurgau have a lot of it and it’s not necessarily representative of a defect. The aromas that are close to this molecule are ivy (Hedera helix), currant, green olive, carnation, green apple or pea…

– 3-ISOBUTYL-2-METHOXYPYRAZINE (IBMP)is famous for winemakers. This molecule, at low doses, can marry other molecules involved in the bouquet complexity. But when its perception threshold is exceeded (15 ng / L), especially in wines from Cabernet Franc, Cabernet Sauvignon and Sauvignon Blanc, then we will have the sensation of biting into a green Pepper ! You’ll understand Bordeaux wines are likely to be heavily affected by this lack of maturity. Capsicum annuum, green pepper, is a chili vegetable and is not spicy. Its taste is very powerful, similar to ivy, moldy earth and peat. What a program ! 

2) Defects due to poor health condition or wine mismanaged 

Defects due to a lack of maturity are sometimes induced by vintage (harvest obligation to prevent bad weather for exemple). But all defects due to poor health status of cellars and tanks are truly attributable to humans in some cases. In general, these defects are caused by rot : the use of unwashed tanks, defective barrels, contaminated product for treatment treatment may be the cause. The grapes affected by Botrytis can also have serious flaws. So long live to beetroot, fresh mushrooms, humus, camphor or wet earth tastes ! Nevertheless, some of these tastes can disappear during the vinification but others will remain and even increase.

– GEOSMIN… So here it’s a real disaster ! This is the king of this family default of this family. Its taste is the wetland. This molecule appears when there are fungi (Penicillium expansum in particular) or bacteria that contaminated water especially. Thus barrels or poorly cleaned plugs can be a source of contamination. Most of the time though, geosmin is already present in the bloom affected or partially affected by any botrytis grapes.

– 1-OCTENE-3-ONE: with this molecule you will have a wine which tastes Paris mushroom ! Agaricus bisporus (Paris champignon) grows naturally everywhere in Europe : it’s not a very nice taste in wines. It’s an indicator of the evolution of wine and can be found in red as in whites, rosés and even from rotten harvest affected by botrytis wines ! The aromas are close to yeast, oak moss or even the undergrowth tastes.

– 2-METHYLISOBORNEOL: it’s part of molecules having earthy/camphor tastes : it affects only black grapes with botrytis cinerea (noble rot which is famous for Sauternes but which is not sought on the black grapes). Often confused with geosmin, this molecule disappears, except in wines from Pinot Noir. Then the wine acquires very persistent flavors of humus or camphor. 

3) Defects due to volatile phenols 

Volatile phenols are part of the wine microbiology and give a relatively known character : the animal side of some wines. The most famous molecules are vinyl-4-phenol and vinyl-4-guaiacol (higher in whites) and ethyl-4-phenol and ethyl-4-guaiacol (higher in red wines). Both are smelly vinyl-4-phenol (gouache, pharmaceutical odor) and ethyl-4-phenol (stables, horse sweat). In contrast, vinyl-4-guaiacol (pink pepper) and ethyl-4-guaiacol (smoky, spicy) are much less unpleasant even if they are always coupled with their sidekick phenol.

– ETHYL-4-GUAIACOL + ETHYL-4-PHENOL (Brett) : this combination is the bane of winemakers. Brett taste is predominantly found in red wines, but it can also be associated to the “taste of mouse” in white wine (with vinyl)… Brett for short, is the Brettanomyces yeast… The taste is characteristic of horse sweat. Close to this molecule tastes we have castoreum, leather, narcissus or peat. Horse sweat or gouache for some, it’s known as strong animal smell. Able to hide the intensity of the other flavors of the wine as a mask, Brett can be felt even at very small concentrations. However, one side advocates animal touch of wine, for which a little Brett does not hurt and the other side is screaming at defective scandal ! You will choose what you like, but it’s certain that the presence of Brett is a significant breach in the cellars (barrels poorly cleaned, lack of SO2, not complete alcoholic fermentation). 

4) Defects caused by sulfur compounds or reduction 

Sulfur derivatives are characterized by unpleasant odors… Their perception threshold is relatively low (not a lot feels bad). These sulfur compounds are called mercaptans and they are developing during alcoholic fermentation (by yeast) in general. Let’s take a closer look :

– METHANETHIOL… You feel this molecule and you’ll recognize it immediately. It has a smell of stagnant water and is found in the reduced wine. Odors close to stagnant water are rubber odors, cabbage and onion ! Not very attractive for wine, isn’t it ? This defect is the result of stagnation or insufficient flow of wine. Lack of ventilation will decompose molecules that will then create this characteristic odor. Therefore, attention to faulty sealing or vinification too safe of oxygen. In the latter case, the yeast will synthesize methionine in methanethiol.

– HYDROGEN SULFIDE (H2S)… Like the egg flavor ? Well, with this molecule, your egg is rotten ! Fortunately, it’s relatively rare in the bottles. Indeed, it’s rather remark during winemaking where it will evolve to other reduction defects (garlic, onion, stagnated). This molecule is a degradation of sulfur-contained proteins and is induced by yeasts. This note of rotten egg can be facilitated by the treatments used in the vineyard, the use of sulfur dioxide or yeasts oxygen deficiency during fermentation and especially the lack of nitrogen during the FA.

– DIMETHYL DISULPHIDE (DMDS)… A nice name for this molecule that gives hints of truffle to wine. Delicacy, the truffle, Tuber Melanosporum, developed particularly in France, Italy and Spain. Extremely expensive, truffles are harvested with the help of dog or truffle pig. Yet it’s a common flavor to wines made from Cabernet Sauvignon, Chardonnay, Grenache or Merlot… You can also experience this very special taste close to cabbage or Paris mushroom in old Jurançons and Sauternes…

– METHIONOLtastes delicious cabbage ! The aromas are close to stagnant water, onion or truffles ! Brassica Oleracea, cabbage is from the south-west of Europe but is mainly grown in China. This reduction problem is huge in the reds : this is a very strong unpleasant molecule. 

5) Defects due to corks 

Certainly the most famous of all defects… The cork taint is dating from the seventeenth century and appears at the same time as the glass bottle. You have to know that 3-4% of the bottles are affected by this ‘evil’, all backgrounds, all names, all colors  a part.

– 2-4-6-TRICHLOROANISOLE (TCA)is our famous cork taint ! Recognizable close odors are the cap, more accurately cork and earthy-musty. Sniffing the cap can help you to identify the molecule that tends to be hidden after the first sniff. The origin is a faulty plug… But how is this possible ? Cork comes from the cork oak, Quercus Suber, found in some French forest and Portugal. The fungus Penicillium can grow on cork and creates Trichloroanisole molecule due to the manufacturing process or storage cap. But it was also found that the fungicides used in the treatment of wood in the cellar (pallets, frames) could also facilitate the emergence of mustiness (which coincides with cork taint and olfactory nature but of different origin). But what is the only way to know if it’s a corked or musty taste ? Well,  if one, two or three bottles on the lot are affected, then it is TCA. By cons, if the whole batch is contaminated, there is surely the presence of mustiness (TeCA – Tetrachlorophenol or TCP or TeCP… full of pretty molecules you fwill orget the name anyway because your bottle is cooked !). 

6) Defects due to external causes 

The use of epoxy resin tanks, plastic pipes, synthetic elastomer but also accidental hydrocarbon pollution are all exogenous causes that can make faulty wine tastes.

– BENZOTHIAZOLE: with its taste of rubber, it’s not the nicest molecule in the wine ! It’s derived from the decomposition of resins or tanks, but more rarely, misuse pumps in the winemaking. Natural latex rubber is derived from, proceeds of an Amazonian tree. Relatively close to the rubber smells are the birch tar or stagnant water.

– P-CRESOL : it smells of peat or birch tar. Peat, it’s in whiskey if you like those of Ireland or Scotland… But in wine, it’s flawed. Often present in the Madeiras, we also feel this molecule in old wines of Pinot Noir or Syrah among others. Coffee, castoreum, oak, birch tar, musty earthy, patchouli and horse sweat smells are close. Peat, as a reminder, is a fossilized wet bodies debrits of plant in wet and low oxygen!

– STYRENEis an aromatic organic compound that comes from tanks with epoxy resin manufacturing with defect. Styrene is used in the composition of plastics, insulators, fiberglass or plastic packaging. It returned to the carcinogens and is today therefore prohibited to use. Styrene has a taste of celluloid or plastic.

– BENZALDEHYDElooks like bitter almond. It’s also used to make cherry spirits smell (cherry stone). A nearby molecule of Benzaldehyde smells hyacinth. Its origin is the resin used as plasticizer tanks but also used as the basis of some gelatins for bonding at the end of vinification.

– ESSENCE: You all know the smell of hydrocarbons. Otherwise, go to a service station and here is the smell your wine will get. Indeed, it may happen that the grapes or the winemaking is polluted via air or directly by the gasoline engine. 

7) Defects due to oxidation 

The oxidation is sometimes sought for certain types of wine (rancid) as the Jura wine or sherry for example, but outside of these families of wine, oxidation is considered as a defect. The wine requires oxygen, especially during alcoholic fermentation, so that the yeast employed can survive and work. But an excessive oxidation (in the bottling of wine or during manipulation of sampling) leads to what is known as the vent. Oxygen removes or transforms some molécules of the bouquet and will create the most famous and recognizable of all : ethanal.

– ETHANALhas a  nice look in fact : it’s the taste of apple. But make no mistake, this is not any type of apple is overripe apple An apple that has exceeded its stage of maturation. Rotting… Brown, all wrinkled. We find this ethanal molecule especially in sparkling wines or white wines. But also in red wines with the excessive oxidation. Odors that come close are the quince, raspberry, walnut, pear and green apple. The ethanal is really recognizable in the mouth. 

8) Defects due to bacterial spoilage.

Say like this, it’s not a good sign… And well it is !

– ACETIC ACID… If you feel this, then unfortunately your wine can be thrown into the sink. This is probably the worst fault of the wine that we can find. Welle it is at least one of the most unpleasant. Indeed, the acetic acid has a taste of vinegar ! Acetic acid is calculated : its dosage should not exceed 0.88 g H2SO4 / L for white wines and 0.98 g H2SO4 / L for red wines. Beyond these thresholds, the wines are unfit for consumption. This acid is formed by yeasts during alcoholic fermentation in small amounts (this is normal), but also by lactic acid bacteria (Pediococcus) during malolactic fermentation (and this is where deviance may occur). In the presence of sweet wort, fermentation may stop or become languid… Lactic acid bacteria will then convert glucose into acetic acid (bite) and fructose into mannitol. Then hello vinegar taste !

– ETHYL ACETATE (acescence): it’s in fact the bite acetic, not to be confused with the previous lactic bite, even if it’s a fault also unpleasant. The acetic bite tastes like nail polish but also gives to the taste an unpleasant burning. There are several acetic acid bacteria, but for the wine it’s Acetobacter the master. This bacteria causes serious defects corresponding to the acescence. The bacteria will oxidize (very important need therefore of oxygen) acetic acid in ethanol. The ‘next step’ is esterified acetic acid in ethyl acetate. The storage conditions of the wine must be perfect to avoid this overflow.

– DISEASE RUNS: this is a fault which is rare in wine but which is induced by lactic acid bacteria. A strain is the cause : Lactobacillus plantarum or Brevi. The bacteria will degrade tartaric acid. Tartaric acid is very important in wine : it can pack a good acidity as well as taste and holding wine. When the wine loses its tartaric acidity, the pH increases and its color becomes dull and brown. The disease makes uninteresting wine with flat and dull taste. The wine is disorder in the glass, but when agitated, appear dancing reflections.

– DISEASE OF BITTER: like the previous disease, it’s caused by lactic acid bacteria. This is the degradation of glycerol and it’s also extremely rare. In order to make appear the disease of bitterness, it’s necessary that the wine is from a weathered vintage and little mature. The wine must have also a low alcohol level : it’s then that the lactic acid bacteria will degrade glycerol in to acetic acid or acrolein (bitterness). So you understand, the wine will have a pronounced bitterness.

– DISEASE FAT. This is the third and last illness that can be recognized. Rare as the previous ones and also due to the lactic acid bacteria (Leuconostoc), it is known as ropy disease wines. Only the appearance of the wine is changed : there is no particular taste or odor. The wines have an oily appearance and the only way to cure this disease is to sulphite and beat vigorously the wine. 

9) Defects due to premature aging of wine 

If you need to remember a word about premature aging of wine, it is Premox (‘premature oxidation’). White wines and red wines are affected by this ‘evil’. White wines will lose their acidity. Fruity aromas of their youth will disappear in favor of heavy flavors such as honey, wax, naphthalene, acacia flower or resin. The color of the wine will take on a bold yellow and bitterness will be relatively present. Odor of reduction of old dry white or sweet wines as burnt notes, mineral and truffle are enjoyable and we must find them naturally. As for red wines, premox will give tastes of prune, fig or cooked fruit and will mask the fresh fruit notes.

Causes of premox vary depending on the color of the wine ! For white wines, the small amount of glutathione (sulfur peptide with antioxidant properties) synthesized by yeasts will increase the risk of premox. More glutathione is in large quantities in musts, more the water and nitrogen supply in grapevine is correct. For red wines, the lack of anti-oxidants is also the major cause of premox : little tannin wines will weaken as a lack of SO2.

– SOTOLONis very recognizable with its taste of curry, fig and walnut. Sotolon molecule is the best known note of evolution for red and white wines. Wanted in wines such as sherry or Porto, it’s a common premox. Unfortunately, like most (if not all) molecules encountered, there is nothing to do once it’s detected in the bottle. By cons, during winemaking, keeping white wines on the lees can preserve the youthful aromas and avoid the formation of sotolon.

– METHIONALtastes like boiled potato or soy ! Somewhat unusual, isn’t it ? Close tastes are soybean or oak, caramel, toast, licorice or cocoa. Rather friendly flavors, you will tell me ! Very present in the Madeiras or sherry, it is also possible to perceive this molecule in premox white wines. Soybeans are native to warm regions of south-east Asia. But it’s also grown in the USA and South America. The most common form is the soy sauce.

– PHENYLACETALDEHYDE: this molecule feels faded pink or honey. It’s present in white wines and flavors associated are hay, broom, jasmine and narcissus. Pleasant smell of beeswax : it is known in the mythology with Icarus myth. Unfortunately, as the poor young man, wine with flavors of beeswax honey is synonymous of premox. Rosé or white can be touched… A major premox !

– 0-AMINOACETOPHENONElooks like mothballs or encaustic, to choose from ! We find this molecule in white wines… Naphthalene is the product that we put in cabinets to protect clothes against moths ! And polish is the dissolution of beeswax with turpentine ! It’s powerful odors that take over the wax and tar.

– GAMMA-NONALACTONEtastes cooked fruit or prune in red wines. This is the most recognizable of premox aromas in red wine. Prune is the fruit of plum or Ente Agen plum (the best known). We find this molecule in Portos or Reciotos. It’s really a characteristic flavor that will make you understand that your wine is more mature than it should be. Aromas close the Gamma-nonalactone are dried banana, quince, raspberry jam, chard apple and raisin.

– 3-METHYL-2,4-NONANEDIONEdevelops flavors of anise and dried herbs. This molecule is naturally found in the green tea or soybean oil. The smell is also close to beeswax, green tea, black tea or eyelet (among others). This molecule is present in some young wines and Pineau des Charentes but in general it’s associated with premox of red wines !

So I hope that it’s a good listing of the major defects that you can find in the wines. Of course there are others ! Pro cork taint, now you’re as pro for other flaws ! And if you want to train, you can acquire the Nez du Vin, Special Defects ! Good luck in the jungle of wine !

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