Wine is a “living” product involving the use of oxygen, bacteria and yeast in its production. If the levels of these are not managed correctly by the Winemaker, faults may occur in the finished wine. Here is a brief guide:
What Are The Main Wine Faults?
Oxidation, High Sulphur Dioxide, Reductive Odours, Volatile Acidity, Corkiness and Microbial Spoilage cover most of them. Corkiness is by far the worst culprit followed by oxidation – the others are, thankfully, much less common.
What About Those Gritty Crystals?
These are potassium or calcium tartrate. They are naturally occurring, tasteless and harmless. They are not a fault. They crystalise when a wine is kept at low temperatures for more than a few days. Many large retailers insist that winemakers chill their wine to the extent that the crystals precipitate and can be filtered out before bottling. The danger here is that although the crystals are removed, some of the character of the wine disappears too. Tartrates, like sediment in red wines, should be seen as a positive indication that the wine has not been tampered with too much. Just be careful how you pour the last few drops from the bottle and you won’t have any problems.
What is Oxidation?
Too much oxygen in contact with the wine, either at the winemaking stage or once the bottle is open. Some oxygen is good, especially for red wines which soften once opened and allowed to “breathe” - but too much can cause problems. Winemakers protect wines from too much oxygen by using Sulphur Dioxide. Most red wines react well to the oxygen in the air once a bottle is opened – some may even taste better the following day – but older, more fragile, wines can oxidise very quickly. Check with your Wine Merchant if you are unsure whether to allow a particular wine time to breathe.
How Will I Spot an Oxidised Wine?
White wines darken in colour, lose fruit and take on a nutty, sherry-like taste that lacks freshness. Reds go brown, lose fruit and develop an excessively dry feel in the mouth. Next time you have an inexpensive bottle of white wine, leave the last inch in the bottle, with the cork out, for a few days and taste it again – that’s oxidation. Some people refer to the wine as being madeirised since it can smell reminiscent of madeira. If a wine is “Ullaged” it may well be oxidised.
When the level of wine in the bottle is low the wine is said to have “ullaged” . This means some wine has escaped and this may well be evident on the capsule and cork. If wine has got out then air has probably got in.
What about High Sulphur Dioxide?
Very simple – a wine where too much Sulphur Dioxide has been used by the winemaker. Almost all winemakers use it as an antioxidant but it can hang around on the wine and still be evident when you pull the cork. It generates a prickly sensation at the back of the nose/throat which may cause sneezing if you are very sensitive – some people even complain of severe headaches though the alcohol tends to complicate the process of identifying the true culprit! It is harmless and a necessary part of vinification hygiene, but too much is a fault.
What Are “Reductive Aromas”?
Stinky, rubbery, bad egg smells caused by the combination of sulphur and hydrogen in the absence of oxygen. This sounds a bit like a chemistry lesson but the oxygen in the air can be removed by the yeasts if the fermentation takes place too quickly (in a hot climate for example). Problems like this can be rectified before bottling if spotted in time, but eventually become irreversible.
Is This What People Mean By “Bottle Stink”?
No. Bottle Stink is a very mild reductive aroma which you notice when you open the bottle but which clears very quickly. It will not spoil your enjoyment of the wine in question. It is most likely to be encountered in older bottles.
What is “Volatile Acidity”?
A minefield! All wine contains volatile acidity to some degree but too much is a fault. At low levels volatility lifts the aromas and adds complexity and it’s all a question of balance. Volatile acidity is acetic acid and is a natural product of the fermentation. As a fault, it is much less common than it used to be due to improved winery hygiene and the ability to control the fermentation temperature. It generates an aroma of pear drops in low levels, but can make wines smell of nail-polish remover (acetone) if severe cases.
When Is A Wine “Corked”?
When the cork has reacted with the wine and imparted a musty aroma and flavour. The culprit here is a compound called Tri-Chloro Anisole which can contaminate anything like cork, wood, or cardboard. In its worse form it is very easy to spot and the wine trade generally has seen moves towards alternative ways of sealing a bottle of wine (see Factsheet no.1). What is more concerning are those bottles where the corkiness is much less evident. In these cases the wine just tastes flat and lifeless and the consumer may simply regard the wine as poor, and not buy it again, rather than identifying the fault.
How About “Microbial Spoilage”?
Not surprisingly, this is where the wine has been spoilt by bacteria. For instance, the yeasts should all have been removed before bottling, but if any remain there is a chance that they will re-ferment any residual sugar and generate unwelcome carbon dioxide, alcohol and sediment. Lactic and/or acetic bacteria may also cause problems. Secondary fermentation is easy to spot because the wine is fizzy when it shouldn’t be. The yeasts will also make the wine cloudy.
Muscadet and Vinho Verde Are Often Cloudy – Is This A Fault?
No. This effect is caused by tiny bubbles of carbon dioxide which are a deliberate part of the character of such wines. The bubbles will be visible when the wine is poured, but will clear quickly. If a wine stays cloudy and dull in appearance there may be a problem.
Anything Else I Should Know?
Yes. Some perceived faults are not faults! The slight sparkle called “spritz” in some crisp, dry whites is deliberate. If bits of cork crumble off and end up in the wine this does not mean that the wine is corked! This may sound a bit obvious but you would be surprised how many people get this wrong. Sediment in red wines is a natural occurrence and is a good sign that the wine has not been over-filtered before bottling; it means you’re drinking it as the winemaker intended rather than a “cleaned-up” and lifeless version designed to sit on a supermarket shelf and never throw a sediment. We’ve already covered tartrates which can be anything from a fine grit to a veritable snowstorm. They are occasionally inconvenient, but nothing is wrong with the wine. You may also discover some mould on top of the cork when you remove the capsule – this is caused during bottling when drops of wine get trapped on top of the cork when the capsule is applied. They then go mouldy, but don’t worry, what you’re interested in is on the inside of the bottle so just wipe this off.
What’s The Most Serious Fault Of All?
Easy. When the cork is out of the bottle but no wine appears to be inside. This is most serious and means that your bottle is empty. Thankfully, it is the easiest to rectify!
What Do Wines of Interest Think?
We taste many wines in the process of putting together our lists and offers. We estimate that for every wine we list we reject 40. Some of these are faulty, others poor and many more simply uninspiring. Consistent faults are weeded out at this stage so that you will only encounter those that occur indiscriminately such as the odd rogue corked bottle. We will, of course, exchange obviously faulty bottles but we do need to have them returned quickly before they are overwhelmed by oxidation which will hide anything else that might have been wrong with them. There is, of course, a difference between a wine having a fault and you simply not liking it and it’s only through regular tasting that you’ll get to spot the difference!