Faults and Flaws
Faults- do not continue drinking, discard the wine, many shops will replace or refund a faulty bottle.
Flaws - are less serious and can affect the sensory properties but are still OK to be consumed.
Cork Taint
‘Corked’ wine is a common term, however many people don’t understand what this relates to. It actually refers to a chemical compound called 2,4,6- trichloroanisole, this is better known as TCA. TCA can enter a bottle of wine in a variety of ways either from the winery or from the cork itself - hence the name. Since the compound can be introduced during the wine's production (within barrels or in the equipment) it can also affect screw cap wines. Many people do not appreciate that this can occur. The signs that TCA has affected the wine are musty aromas similar to wet dog, mould or wet newspaper. If you continued to drink the wine you would notice that the fresh fruit characters were no longer present and only a flabby, off-tasting wine would be left. Cork taint is normally easy to notice and a fault in wine therefore the bottle should be discarded.
Sulfur
(Or Sulphur depending on who you ask!)
The majority of wine contains sulfur dioxide, it is used as an antiseptic and antioxidant (reducing the affects of oxygen). Unless you specifically seek out sulfur-free bottles, your wine will have had contact with sulfur dioxide. The problem doesn’t lie with this compound but instead a chemical produced during fermentation that creates hydrogen sulfide (a similar structure where the the two oxygen’s have been replaced by two hydrogen atoms.) This compound can then go on to produce other Dimethyl Sulfide and Mercaptans. The three chemicals create the signature fault smells of rotten eggs, cooked cabbage and rubber. At low levels some people can overlook this flaw however when particularly pungent the signature's aromas will be lost and the wine ruined.
Light- UV
Ultra violet light which is generated by the sun can cause damage in wine. This is a factor to be considered on the storage of wines as it can reduce stability and negatively impact on colour, flavour and aromas. This occurs as the UV light encourages pigment breakdown. Wines will have the aromas of wet clothing especially woolly jumpers or wet cardboard and the colour intensity will also be significantly reduced.
See Storage of wines for more information
Heat
When the temperature of a stored wine fluctuates the damage can be seen within the wine. High temperatures can cause the wine to taste ‘cooked’. This flaw will produce jammy flavours rather than the typical fresh fruit tones. Often caramelised sugar or toasted nuts can also be smelt. This is a flaw rather than a fault and although the wine will not be at its best it will not cause harm. A second and more harmful consequence from drastic heat change is the potential damage to the seal leading to oxidisation (see below).
Oxidation
Contact with oxygen can cause extreme damage to wine, it is also the most common flaw. This is because the oxygen molecules react with compounds in the wine e.g. phenols causing oxidation leading to a loss of aroma, flavour and colour. Slow oxidation will occur in older wines, hence garnet and tawny colours can be seen in red wines and the primary flavours will have moved in the tertiary direction. White wines oxidise more readily due to the lack of tannins and colour change can easily be seen. Flavour characteristics will turn from fresh and fruity to dried, or cooked fruits and nuts and bitter tones. See the section on storage for information in how to reduce oxidation once the wine has been opened, however, if the bottle is oxidised when opened it is best not to drink.
Key terms
Phenols- an organic compound with an -OH group attached. In wine they affect the mouthfeel, flavours and colours produced.
Garnet, tawny see The Aroma, Flavour and Colour Kit
Primary, tertiary characteristics see The Aroma, Flavour and Colour Kit
Volatile acidity
This is when a wine is affected by acetic acid bacteria, these microbes produce the acetic acid compounds. It is also more commonly referred to as vinegar taint, which gives a good guide as to the affect it has on the wine, producing aromas similar to nail polish and vinegar. These qualities are rarely desired however, some winemakers incorporate some acetic acid into their wine in order to produce more complex flavours and some people enjoy these characteristics. This is a flaw rather than a fault and the wine can be used in cooking or salad dressings rather than being thrown away.
Key terms
Microbe- Single celled organisms found everywhere, often in the form of bacteria. The term microbe is often linked with causing fermentation or disease.
Brettanomyces
More commonly referred to as ‘Brett’ is a yeast that produces compounds in wine. The difference in compound produced corresponds to the flavours that arise. Three broad categories are recognised and then split into individual flavours: vinegars, medicine (antiseptic) and most commonly animal (horses stable, mushroom, cheese). Many people find small levels of this very pleasant and will happily drink an affected bottle. It is preference dependent but the wine is still safe to drink.
Tartaric acid crystals
Tartaric acid is often added to wine to increase acidity levels within the wine. Countries that are warmer often struggle to retain acidity and find their wine can become flabby and unbalanced. Occasionally this compound can precipitate and form tartaric acid crystals. They are usually transparent and colourless unless they have absorbed the wine's colour. Completely harmless, they will not affect the quality of the wine and are easily left behind in the bottom of the bottle or thrown away with the cork. If any do slip into the glass try not to chew them as they can cause damage to teeth!
Key terms.
Precipitate a solid produced in a liquid e.g. a crystal.