Top 6 Wine Faults: Their Causes & How to Identify them?
Our infographic helps you learn about the most common wine faults, how to identify them, and what causes them. We’re also giving tips on how to eliminate some of them, or temper their negative effect.
Wine faults are a pain in the neck!
One carefully buys wine, spends money on it, sometimes stores it for several years, and looks forward to opening the bottle and please guests, only to find out that the beverage is not at its 100%, if not undrinkable.
Unfortunately, they are unevitable. Wine is a living product. Like humans, it can never be perfect, and mistakes do happen. This is the beauty of it, but also its downfall.
There is a lot of talking and a lot of mysticism around wine faults.
Many self-proclaimed wine connoisseurs, even wine professionals will pretend to have identified a fault that is not one, put the wrong name on it, or invent solutions for eliminating them that only work in their mind.
There is science behind wine faults, their origin, their chemistry. There are also simple aromas that allow to identify each of them accurately.
If you think wine faults are complicated and hard to detect: change your mind, read on, and take our infographic with you at your next wine tasting.
In the real world, there are 6 most common wine faults. This is what they’re about:
Cork taint / TCA
What is TCA?
Trichloroanisole or TCA is a natural compound most-generally found in wood that has been in contact with some form of chloride chemical.
When Chlorophenols, molecules found in certain pesticides and wood preservatives, get in contact with wood, they can be transformed by fungi into TCA and other bad smelling agents. Because most of the wood surrounding us is treated with preservatives —so it doesn’t rot—, the contamination comes from anywhere.
If a contaminated wood gets anywhere near wine, the bad odours concentrate into the wine until it may eventually become ‘tainted’.
Main source of TCA in wine is obviously the cork for 2 reasons:
- A cork is essentially a piece of wood (or bark to be precise) that comes from a tree (the majority of cork trees used for making wine corks are grown in Portugal). If that tree has been in contact with chloride compounds at any given time in its life, its bark may have developed bad smells
- A cork is obviously in close contact with wine, allowing bad aromas to contaminate the liquid.
But TCA may also have contaminated the wine before it was even bottled if affected wood was present at the winery (in timber or pallets for example). TCA may even get from the outside into the wine through the cork if the bottle is stored in a TCA-rich environment (e.g. a contaminated cellar).
How to identify cork taint?
A strong smell of wet cardboard, wet newspaper, or intense mushroom odour is what you’re looking for.
In addition, if it really is TCA, all other aromas and flavors in the wine (fruit, oak, spices, etc.) should be difficult to smell and be hidden in the background.
Aged wine can develop some mushroom aromas that can be confused with TCA. How you can tell the difference is that without TCA, you should still smell many other flavors, spices in particular.
Tips to eliminate TCA?
Unfortunately, if a wine is tainted, there is no way to improve it other than taking it back to the shop or dumping it down the sink. If any accessory manufacturer pretends his product reduces the impact of cork taint: they’re lying!
Make sure you don’t store your wine in a room that contains old wood however, as it may contaminate the wine.
Brettanomyces a.k.a. “Brett”
What is Brettanomyces?
Brettanomyces is a yeast of a different genus than the one we like that runs the alcoholic fermentation (Saccharomyces). Brett as it’s often nicknamed ‘Brett’.
It can grow in the wine and synthesize bad smelling compounds, volatile phenols to be precise.
Brettanomyces yeasts are virtually present in every wine. In fact, it has been found that they are already present on the grapes in the vineyards before they even make it to the winery. But most generally, their population in the wine remains too small for them to generate enough bad smelling molecules to spoil the wine.
Sulphur dioxide added to wine helps maintaining the Brett population at a low level. One of the reasons SO2 preservative is added to wines.
How to identify Brettanomyces?
No wonder why vinyl is often used to describe Brett’s odour. Some of the phenols responsible for the smell have a similar chemical structure to our good-old disc records (vinyl-phenols).
Some paints contain volatile phenols as well, so the smell can be associated with paints.
Wild game, horse sweat or stable are the most common descriptors.
Tips to eliminate Brett?
Again, I am afraid I can’t help you here. There is no way to eliminate or reduce the smell once it’s there.
Like for any particular odour though, some people smell it more than others. The variability in smelling sensitivity in regards to one particular molecule between different individuals can go from 1 to 100. In other words, for the same odour concentration, one person may smell it at a level-1 intensity, while another may smell it 100 times more.
If you smell Brett intensely in a wine, give it to someone that smells it 100 times less! He/she won’t mind it. Your friend might even enjoy the extra complexity and savoriness given by a little gamey animal character.
What is Reduction?
Reduction is the opposite of oxidation.
With oxygen, wine oxidizes. Without oxygen, wine reduces.
Because wine is famously full of anti-oxidants, it tends to absorb all traces of oxygen. This is generally a good thing, with health benefits and a natural ability to sustain oxidation.
But during fermentation, yeasts actually like a little bit of oxygen. If they don’t have any at all because the winemaker doesn’t aerate the wine at all, yeasts compensate by transforming sulphur compounds naturally present in every food into bad smelling molecules.
How to identify reduction?
The bad-smelling compounds that form the reductive character of a wine, are the same as the ones found in eggs (especially rotten ones) or cabbages.
Smelly plastics like rubber or tires are also full of them. So that’s what reduction in wine smells like.
Fetid waters are also reductive media, so they develop an odour of reduction.
Tips to eliminate reduction?
Aerating the wine will oxidise the reductive compounds, making them odourless.
This can be achieved by opening the wine in advance, decanting it, pouring it out of the bottle and back in, or simply leaving it breathe in the glass for a while.
Find out more with our Beginner’s guide to decanting wine.
What are mercaptans?
Mercaptans are sulphur compounds like the ones described in the section about reduction, but that are bound with other molecules in the wine. This generally happens when a wine suffering from reduction has been bottled with all the reductive compounds in it, without prior aeration to solve the problem. The small sulphur molecules react with bigger aromatic compounds in the wine and bind with them.
How to identify mercaptans?
Because sulphur can bound with many different aromas in the wine, mercaptans can smell of many different sulphur-rich foods like cabbages, garlic or onion.
Tips to eliminate mercaptans?
Once the sulphur has reacted with bigger aromas in the wine, aeration won’t make them odourless.
Drop a coin containing copper (the bronze-like ones, not the silver-like ones) in your wine glass and agitate for a minute. The coin will absorb the mercaptans, making all other flavors available for your nose to smell again.
What is volatile acidity?
Volatile acidity (or V.A. as winemakers refer to it) is called this way because it is made of acids that can ‘fly’, that are volatile.
Most acids can’t ‘fly’ or can’t evaporate out of the liquid they’re into, even if warmed up or boiled. Volatile acids can.
Volatile acids primarily come from the oxidation of alcohol by bacteria. These acetic bacteria feed on the alcohol in wine, and transform it into vinegar.
Have you ever noticed that cooked vinegar (e.g. a vinegar reduction) is a lot less acidic than raw vinegar? That’s because the aggressive acid has evaporated out of it. Put your nose over a hot pan and through vinegar in it. You will feel the volatile acidity evaporating.
How to identify Volatile Acidity?
Essentially, vinegar is full of volatile acids so that’s what V.A. smells like.
A wine with high volatile acidity, is a wine that is on its way to turn into vinegar, its natural fate.
Nail varnish remover is full of acetate, a form of volatile acid. So it smells like some high V.A. wines.
Tips to eliminate Volatile Acidity?
Well you could boil the wine and that would do the trick. But the wine might not smell quite like itself afterwards.
Chilling the wine is the best option. It won’t entirely solve the problem, but the volatile compounds will evaporate less at low temperature, so they will be less bothering.
What is oxidation?
When aromatic compounds get in contact with oxygen, their chemical structure is modified, changing their smell.
Oxygen typically gets to the wine through the cork. Oxidation happens if the cork has some structural defects or dries up while the bottle is left standing. High temperatures accelerate oxidation hence storing wine in cool places is always better.
How to identify oxidation?
Oxidation converts normal wine aromas like fruit aromas into less enjoyable ones.
As an example of standard wine aromatic profile when it’s not oxidised, see our Infographics & Guide to Chardonnay wine grape variety.
Oxidation generally translates into flavors of green apple, walnut or fennel.
Tips to eliminate oxidation?
Once the wine is oxidised, there’s no remedy unfortunately. It’s irreversible.
But storing your wine is cool and dark places will prevent it. Don’t allow the cork to try up by leaving the bottles lying on their side.
And don’t buy the bottles that have been standing for too long at the wine shop.