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How to Spot Faulty Wine

Have you ever wondered what you're supposed to do when the restaurant waiter, or the sommelier if you're moving up in the world, pours you a taste? It's simple; it's so you can send it back if it's faulty. The problem is, how do you know when a wine is faulty? Here The Winedoctor describes the most common faults with wine.

Knowing your way around wine isn't only of use when in a restaurant. Wine purchased from supermarkets and merchants is just as likely to be faulty. If you can spot such defective wines, as a consumer you are well within your rights to return the bottle to the store and request a refund. Under British Law, goods must be of "merchantable quality", and if not the retailer may not refuse a full refund, regardless of your probable inability to produce a receipt.

I once returned two bottles of wine to a well known and generally well respected UK wine retailer, which has a national chain of outlets. I had originally purchased three bottles, but didn't get around to opening the first until over a year later. It was an awful, "cooked" wine - it had clearly been exposed to high temperatures at some time since bottling. This had happened prior to my purchase of them - I should have known better, as the tell tale signs were there (see below). After deliberating for a while, I decided to return the other two bottles to the shop (I could have returned all three, but I had thrown the first one away). Despite the passage of time, and the lack of receipt, the retailer graciously offered a full refund. I left the shop a happy customer.

But that's not where the story ends. Being a frequent visitor to the store in question, imagine my horror when I spotted the very same bottles on the shelves, for sale, only a week or so later. I would never have bought them again - I'd learnt to spot the bad bottle. But would you buy them - and if you did, would you spot they were faulty?

The Corked Wine

Wine wouldn't quite be the same if it all came in screw-capped bottles. It would, however, be free of cork taint. A wine is corked when it has been in contact with a cork infected with a fungus that produces 2,4,6-trichloroanisole, otherwise known as TCA. It is this chemical, rather than the fungus itself, that imparts the unpalatable flavours to the wine. For years now the wine industry has been dogged by cork taint, and possible solutions include screw caps, beer bottle caps, man-made corks and cork sterilisation using microwaves. Nevertheless, cork taint continues to spoil up to 5% of all bottles of wine.

How to avoid buying one: I'm afraid other than sticking to bottles with screw caps or man-made corks, you'll just have to take your chances with the rest of us!

Pieces of corkHow to spot one: As with cooked wines, corkiness may appear in a spectrum from barely noticeable to very obvious. A corked wine is not one with bits of cork in it, as shown here! A subtly corked wine may appear fruitless, a little unbalanced, uninteresting, but without any definite signs of cork taint. Leaving the wine for a few hours, or even days, may make the unpleasant aromas characteristic of a corked wine more apparent. By this time, however, it's likely you've either drunk it or poured it down the sink. More obviously corked wine has aromas of wet cardboard, mushrooms, mould and smelly socks! The palate (if you get that far) will taste similar, will lack fruit, and is often quite bitter.

The Cooked Wine

This, in my personal experience, is one of the most common wine faults. That's because it relates to something that's very common in the wine trade, that being poor storage conditions. In particular, the exposure of the wine to high temperatures, this being most likely after it has left the careful hands of the producer, and before it reaches your loving care.

Wine that languishes in the loading bay on a hot summers day, or spends days sweltering in the back of a truck or the cargo bay of a ship, is obviously at risk. And it's not safe when it reaches the retailer - I can recall many forays around wine shops that were uncomfortably warm, when cool air conditioning would have been much more appropriate. And delivery from the retailer can be risky, even from the more reliable businesses that use overnight next day delivery.

When a wine is exposed to high temperatures, the liquid expands and several things may happen. The expansion of the wine may force the cork from the neck of the bottle, pushing it up under the capsule. Or the wine may expand and leak around the cork. In either case, when the liquid cools it will contract, and this may result in air seeping in around the cork leading to a further problem, oxidation.

How to avoid buying one: Never buy a bottle where the top of the cork doesn't sit flush with, or below the level of, the mouth of the bottle. A cork protruding from the bottle, even by a short distance, is a sure sign of a cooked wine. Another test is to try and turn the capsule. It should spin freely around the neck of the bottle. If it doesn't, it may be because it is held fast by the sticky residue that has resulted from leakage of wine around the cork. And if you inspect the level of wine in the neck of the bottle, it shouldn't be too low. There's always some slight variation between bottles, but for everyday wines the level should be well into the neck.

How to spot one: Cooked wines taste just like that - as if they've been cooked. There won't be any freshness to the fruit aromas or flavours - instead you'll get a stewed, prune-like profile. If you're getting blackcurrants and fresh summer fruits, for example, then you haven't got a cooked wine. On the palate, the wine often seems thin, lacking body and character. As with all wine faults, there is a spectrum of severity, and some wines may be borderline, leaving you wondering "Is this a bit cooked?". But if you get a full-blown one, you'll know it. Send it back!


Oxygen is thought to be important in the development of wine. The interaction between the wine and the small amount of air behind the cork, over many years, may be one of the mechanisms by which wine develops when in the bottle. It may even involve minuscule amounts of air seeping past the cork over time. Should the wine come into free contact with oxygen, however, whether during careless winemaking, or due to a faulty cork, rampant oxidation will rapidly ruin the wine. Oxygen is an aggressive element, and will interact with most substances, resulting in their degradation. It's what makes steel turn to rust, turns butter rancid and freshly cut apples brown.

How to spot one: Fruitless wines with a flavour profile resembling old and worn out Madeira or Sherry may well be oxidised. Another term used to describe an oxidised wine is madeirised. This is because Madeira, a classic fortified wine from the Atlantic island of the same name, is made in large open, often outdoor vats. Oxidation here is part of the style of the wine, rather than being a fault.


A commonly used preservative, the addition of sulphur dioxide is practiced by many winemakers. Used judiciously, it can help stabilise the wine during the winemaking process and thereafter. Used carelessly, an excessive amount of sulphur will produce fairly characteristic aromas and flavours.

How to spot one: A wine that reminds you of mothballs, burnt matches or burnt rubber has probably been subjected to a heavy dose of sulphur dioxide. An exception is the ageing Syrah from the Northern Rhône, which with bottle development will often have a rubbery element to the nose that is a characteristic of the wine, rather than the result of sulphur.

Sediments and Crystals

Neither of these are true faults, but both have the potential to spoil the experience unless they are understood. Sedimentation within the bottle is a natural occurrence in many wines, generally those designed to withstand some ageing, and it simply reflects the solid matter settling out of the wine. If poured into the glass it can be pretty unpleasant, and if this were to happen in a restaurant it would certainly be a cause for complaint. The wine should have been decanted.

Tartrate crystalsThe most common crystals found in wine are tartrate crystals (specifically potassium hydrogen tartrate - shown here), and these are often found adherent to the underside of the cork, or in free suspension. Wines that have been cold stabilised by the winemaker have been chilled in order to bring these crystals out of solution so that they may be removed. If this is not done, they may form later in the bottle, especially if kept in a cold cellar. They are of no concern, although they are again unpleasant if taken into the mouth, particularly if large when they may be mistaken for shards of glass.


To conclude, modern winemaking has done much to keep the majority of wines sold today consistent and free of faults, even if the wine isn't to everybody's taste. But faulty bottles still come along, particularly cooked or corked wine. Sometimes they are obviously not right, and it's just a matter of returning it to the waiter, or shop where you bought it. It's the more subtly flawed wines that are difficult to judge, and here it takes a degree of courage to complain, particularly in a restaurant. If you spot a wine that resembles one described above, however, do speak up. The chances are the staff know less about wine that you do, and it's likely that you'll be offered a replacement, even if it comes with the almost obligatory "It tastes alright to me" from the manager.