Ever wondered about flaws, faults and funky goings-on in your wine? Here's a bit about what they are and what causes them...
My favourite wines tend to be those that have been processed the least - 'good wine is made in the vineyard' and all that. But there are risks associated with the so-called 'minimal-intervention' approach. Microbial activity can give rise to all sorts of funky goings-on. You're less likely to encounter such problems in industrially made wines because of processes like heavy sulphuring, micro-filtration and flash pasteurisation. The problem is that these processes will turn what could have been a vibrant, mercurial, multi-layered wine into one that's flat, lifeless - a real Lincolnshire of a wine. And simply no one wants that.
These funky goings-on are expressed by volatile flavour and aroma compounds that run the gamut of eccentricity and reeking horror: horse shit, nail polish, sticking plasters, BO, popcorn, bonfires, blocked drains, tinned sweetcorn, plastic, gunflint... Some will totally ruin a wine, some won't. If the concentrations are relatively low, some aren’t necessarily a problem, they just give the wine a particular slant which you either like or you don’t. But to them all applies the truth that the same wine without such influence would be better. That's because they tend to obscure the character of the grape and the terroir. The notes below will help you to identify and understand the most common faults/flaws/taints you might find your glass.
Volatile acidity (VA)
Volatile acidity, or VA, is common in wines that a) have had little or no sulphur added to them, and b) undergo long fermentations. Basically it's a sign that your wine is turning into vinegar, but it depends on the concentration. Low concentrations might not register, but above a certain threshold and it's going to smell like a bottle of Sarson's. VA is detectable in two basic forms: first, as ethyl acetate, which smells like nail polish; second, as acetic acid - vinegar... At low levels VA is generally tolerated; sometimes it's positively encouraged - eg, in Chateau Musar, a wine whose prominent VA character is loved by some, loathed by others. Amarones often have perceptible VA owing to their long ferments. In properly natural - ie, no added sulphur dioxide (SO2) - wines, it can sometimes be off the charts, which is unfortunate because it makes everyone think that that's how natural wine is supposed to be, when it really isn't.
Uncontrolled oxidation is never good. It will flatten a wine, typically replacing its fresh, fruity character with notes of bruised fruit and a weird nuttiness. The latter is associated with acetaldehyde, which is what oxygen converts alcohol to. If your wine is tasting vaguely 'sherried' (after the bottle has been left open for too long, for example), it's oxidised and there's nothing you can do to rectify it. Best to use that wine to cook with. Note that 'oxidised' is different from 'oxidative' - oxidative wines are made with deliberate, controlled exposure to oxygen and give us wine styles like oloroso Sherry, Madeira, Rancio Sec, etc. 'Oxidised' is when oxygen has run amok.
In Roussillon, they make rancio sec in demijohns which are left out in the open air with a bit of space at the top of the vessel. The combination of (limited) oxygen transfer and heat from the sun maderises the wine.
Reduction isn't the worst thing that can happen and is often easy to remedy. In basic terms you can think of oxidation and reduction as opposites. Oxidation reactions happen when oxygen is present; reduction reactions happen when it isn't.
Reduction produces volatile sulphur compounds which can create a cornucopia of weird smells: rotten eggs, popcorn, blocked drains, overcooked cabbage, onion, gaspipes, gunflint. It's usually caused by yeasts that don't have enough nutrients during fermentation, but it can crop up after fermentation, in barrel and in bottle.
Reduction isn't usually a fault, because usually all you need to do to remove it is aerate the wine and the smell should go away. But if reduction goes too far in the cellar, it can permanently taint a wine. Reduction can also be a winemaking technique. If you're making a crisp, bright, fruity wine, keeping the wine in a 'reductive' state will help you to protect fresh flavours and aromas. It also gives a lovely struck-match character to some fancy chardonnay.
The exposure to oxygen that comes from moving wine from the bottom of the tank to the top - known as 'pumping over' - can remove unwanted reduction.
As the 'myco' suffix indicates, brettanomyces, or brett, is a fungal issue. It's usually controlled by using sulphur. The less sulphur you use and the higher your wine's pH, the higher the risk of brett (the pH thing makes it more of a red wine problem; whites tend to have lower pH). It's one of those resilient microbes that can get almost everywhere - on grape skins, in the cellar environment, in the staves of barrels... Once it's in your wine, you'll struggle to remove it unless you have a reverse osmosis machine to hand. If it's in the bottle, it will gradually come to dominate the wine's 'natural' character. There are two main volatile compounds associated with brett, which produce different aromas and flavours:
4-ethylphenol (4ep) - barnyard, sweaty horse saddle, medicinal (sticking plasters)
4-ethylguaiacol (4eg) - spicy, clove, smoky, meaty
In the past brett was a common feature of many 'Old World' wines - Bordeaux, Burgundy, Southern Rhône and Barolo, for example, which would often smell a bit like a horse's arse. It's usually not too damaging for full-bodied wines, but can be bad news for more delicate ones - pinot noirs for example.
If your wine smells of one of these, blame brett.
Ah mousiness, you total bastard. As with brett, mousiness is typically only a problem in wines that haven't had sulphur added to them and/or have a high pH. It will eventually disappear - after the associated bacteria have metabolised all they can and die off, which may take weeks or months - but it's effect while it lasts is pretty ruinous. It produces a mild but unpleasant taste of wet cardboard, slightly off milk, even, supposedly, mouse cages, though I have't tasted many of those. The way you can tell it's mousiness and not another bacterial scourge is that you can only detect it as an aftertaste. This is because the volatile compounds associated with it don't vaporise at the pH of wine, but do at the pH of saliva - so when the wine mixes with your saliva, the characteristic slightly-off-milk character becomes apparent. As a 'QI' aside: reportedly, up to one-third of people are unable to sense mousiness at all. Also, uniquely, Japanese wine drinkers seem to like it.
Oenococcus oeni - one of the bacteria associated with mousiness.
I inwardly groan when I see people studiously assessing the colour and clarity of a wine. ‘Mid-garnet rim’ - get in the sea. The sediment that causes cloudiness is mostly dead yeast cells, which may sound unpleasant but it can be useful, helping to protect wine from oxidation, especially if it has had little or no sulphur added to it. Of course, sediment needs to be kept to a minimum - no one wants to be drinking sludge - but a little cloudiness is by no means bad. At least you know the good microbial stuff hasn't been filtered out (and if you keep the bottle upright the sediment will stay at the bottom anyway). I'd rather have a cloudy wine that stimulates my senses than a crystal-clear one that rouses no feelings at all. A word on tartrates: sometimes you'll see big, semi-translucent pieces of sediment floating about at the bottom of the bottle. These are tartrate crystals, which can precipitate out of a wine at cold temperatures. They're totally harmless and don't affect the quality of the wine in any way.
Sediment isn't necessarily bad. This is a 'petnat' (petillant naturel) I helped to make in La Palma. With petnat, the wine is bottled before the fermentation finishes, which traps CO2 and makes it fizzy. It also retains sediment, which helps to stabilise the wine, and adds flavour and texture.
Cork taint (TCA)
When a wine is corked it has been tainted by TCA (2,4,6-trichloroanisole), a compound produced from the interaction of certain phenolic compounds with certain mould-type organisms. TCA is transmitted from the cork to the wine itself. It smells musty, somewhere between mushrooms and damp. Usually it's obvious when a wine is corked, and, like other faults and flaws, once you've identified it, it's hard to miss next time round. It varies in concentration, but as taints go, it is the most likely to spoil your enjoyment of a wine.
No flaws with this one...
Here's what you could have won...
The reality is that all these problems are a common in natural/low-intervention wines (with the exception of TCA, which can affect any wine with a natural cork). But there are things a natural/low-intervention winemaker can do to minimise the risk that they will occur. Careful oxygen management and using grapes with low pH both help. It's a bit of an issue when people think they are integral characteristics of natural wine, which they aren’t; natural wines don’t have to be funky, and sometimes the funkiness is a sign that the wine has a problem. Some people like funk, which is fair enough, but it’s good to know what the same wine would be like without it, which in most cases is 'a lot better'. That said, given the choice between a bummy natural wine that’s otherwise lively and interesting, and an industrially made one that's 'clean' but characterless, I know which I'd want to drink.