The first Fringe Event of the 2012-2013 club season was a session on Wine Faults held at Oxford Brookes Restaurant on 5 November.

Our President Michael Palij MW, supported by near-MW Baz Dick (winemaker and Sainsbury’s point man for grower relationships) took 20 plus members through the spectrum of wine faults, using the Nez du Vin aroma kit and a striking range of faulty bottles.

Michael suggested three main groups of faults:

1. Oxygen-related faults (the effect of too much and too little)
2. Bacterial faults such as TCA (cork taint) and fungal faults such as Brettanomyces
3. Wine-making faults (usually stuff that shouldn’t be there such as tartrate crystals; occasionally stuff that should be there but isn’t).

For those who haven’t used it, the Nez du Vin faults kit has 12 tiny glass bottles; each containing a more or less noxious chemical and more or less offensive smell. Very useful for the purpose of building up a library of problematic aromas, but the kit doesn’t – can’t – take account of the fact that most faults are faults only when they are way out of balance with other tastes and aromas.

It’s true that no-one has a kind word for cork taint but ‘green’ or leafy notes (characteristic of New Zealand Sauvignon Blanc) or Brettanomyces characteristic ‘farmyard’ are not necessarily deleterious; they can add to the complexity and richness of the wine – if they are in balance. It’s also true that different individuals have very different levels of sensitivity to different aromas.

So, health warnings over, we got down to some smelly business. First up was vegetal, rather ‘green’, a touch redolent of unripe apples. Not totally unpleasant in itself, but in excess it suggests that the grapes have been picked unripe and often at very high yield levels. It can also be exacerbated by insufficient destalking or excessive pressure during pressing. To show just how fine the line is, Michael had a perfectly sound Oyster Bay Sauvignon Blanc for us to taste. Green pepper, green pea and gooseberry predominated in this bright, sharp wine. The ‘wine that launched a thousand container ships’ he joked. Highly successful and highly commercial. Highly commercial because it’s picked young and at very high yields, up to 15 tonnes per hectare, compared to 5 tonnes per hectare for most quality wines. These methoxy-led flavours are responsible for the green apple flavour in many cheaper Champagnes or Cavas.

Second, the acetaldehyde aroma from the kit characteristic of rotten apples. Alcohol oxidises to acetaldehyde on its way to vinegar. But controlled oxidation is a good thing! Where would Fino sherry be without its predominant acetaldehyde aroma?   There is some oxidation in all wines, but too much flattens the wine stripping out aroma and flavour. The key message from Baz was that the closer you get to the finished wine the more important the control of oxygen. One of the natural controls of oxidation is acidity – think about the way lemon juice stops soft fruits browning – but global warming, a consumer preference for softer, less acidic wines and non-interventionist ‘natural’ wine-making are creating the conditions for more oxidation unless precautions are taken.

The exemplary story is top class white Burgundy in the years 1996-2002. Many of the wines have simply ‘fallen apart’ and don’t have the structure to mature as they should. In Michael’s words, this is a ‘big, unacknowledged problem’ where not just the wine-makers but also the big merchants have been in denial.

The next aroma up was ethyl acetate; typically marked by pear drops, nail polish remover or varnish aromas. This is a marker of ‘stressed’ yeast and / or high levels of acetic acid? In the presence of oxygen, ethanol and the ‘excess’ acetic acid combine to form ethyl acetate. This took us back to the issue of ‘balance’. In many long-established vineyards the indigenous yeasts and bacteria have reached an accommodation that delivers good wine – and that’s why great wine can (sometimes) come out of pretty mucky cellars. But you can’t always rely on the wine righting itself, even when it is made with great care and attention to detail. Michael showed a high class (and high-priced) Italian red where the wine-maker puts in a great deal of effort to use only natural ingredients. That means a low / no sulphur regime and the resulting wine had a distinctly ‘funky’ and, to many people, off-putting aroma. In the mouth it was a different story, sweet and rich with clear fruit flavours and good balance. But only if you could get past the nose.

Sulphur in its many forms is a key weapon in the wine-maker’s kit. Sulphur dioxide (SO2) disinfects and protects, though too much can give the burnt rubber or ‘spent match’ aromas (or the ‘prickly nose’ effect) that often characterises many low acid German Rieslings (German wine-makers, observed Baz, are sulphur fanatics). This excess or ‘free’ SO2 blows off fast but some people have a tendency to get headaches from the sulphur by-products in wine.

Sulphur is added all through the process though there are laws controlling its use to prevent abuse since it can be dangerous to health – particularly for the winery staff – and bad for the wines.

In the absence of a trickle of oxygen (which the sulphur binds to), wines can get what are termed reductive aromas. This is rare with natural cork but particularly prevalent with first generation or less sophisticated screwcap closures. The sulphur converts to hydrogen sulphide (H2S), which gives a rotten egg or bad garlic aroma. These aromas can be dispersed by a touch of copper or by vigorous oxidation – hence the trick of putting a 2p coin into your wine and swirling it around! However, too much copper fining and you start to strip flavour. It’s a balance game…

The next fault we looked at was re-fermentation in bottle. This typically occurs in white wines which have a level of unfermented sugars. Some wines such as Vinho Verde rely on this secondary fermentation to give a spritz to the wine. In most cases, however, sterile filtering is used prior to bottling to remove the possibility of re-fermentation for, alongside the spritz which is the most immediately noticeable effect, you get coarse aromas and occasional cloudiness. It can be mistaken for excess volatile acidity but the key is the mouthfeel.

Brett (technically Brettanomyces) is yet another of those faults which, under control, can add richness and a savoury quality to wine. It can add a bacon / savoury note (often a good thing) but in general manifests itself as a smell of hospital bandages, or ‘sweaty saddle’, or barnyard / faecal taint. Some people have very high sensitivity to this; others less so (or just more adapted to it). We tasted a Rosso del Vulture from Michael’s collection that immediately sparked a debate.... Fault or no fault? And was it saleable in that condition? Most people thought it was – despite the Brett tinge.

Poor cellar hygiene is responsible for many faults, though, as Baz had already pointed out, a winery where you could safely eat your dinner off the floor is no guarantee of perfect wine! Dirty casks – or even a single faulty stave in an otherwise perfect cask can be a problem. In many regions barrels are not renewed as often as they should be giving rise to 2-ethyl-fenchol or the mouldy aroma of wood spoilage, often detected on old Rioja.

High temperatures in the storage area can result in maderisation – another manifestation of oxidation and possibly the cause of the next faulty bottle we looked at – a red wine turning fast into a rose. The protein had separated out from the liquid and adhered to the glass of the bottle. After we had tasted our samples, the bottle we looked at (which tasted pretty much ok) still appeared to be full, though the drunk portion was pinkish and remaining liquid reddish. Careful fining (with Bentonite) or fine filtering should deal with this problem.

Cellar hygiene is also implicated in the last of the faults we looked at – cork taint. A corked wine – not one with a bit of floating cork in it – has an earthy / musty / mouldy cardboard aroma and the wine itself is flat and stripped of flavour. Once again sensitivity varies but even today it is reckoned that around 5-6% of bottles (particularly those with natural corks) are affected. The enemy agent in this case is the compound 2-4-6trichloroanisole (usually abbreviated to TCA). It’s linked to the use of chlorine bleaching of corks and other winery components. Natural cork producers have hugely upped their game in the last decade or so but it’s not only natural corks that are affected. Screwcaps can be tainted (though it’s much rarer) and the strength of the taint is such that affected paper or barrels or roofing material in the winery can spoil the wine. If you detect it, send the wine back! From the floor the suggestion was made that dunking cling film in the affected wine can deal with some of the problem…

In conclusion Michael and Baz came back to three key points. First, all wine-making is natural wine-making. Second, and consequently, balance is everything. Many faults are ‘faults’ only when they pull the wine out of balance. So, wine-making is not a dichotomy between cleanliness and cobwebs. Great wines can come from either environment.

GH: 8/11/12