Basic Wine Faults

Full article on this will be in The Telegraph (Kolkata) next Sunday, 22nd March 2009.

Wine is a living thing and is susceptible to faults, like any other product. There are a variety of chemical and wine-making faults that can occur, either in the winery or while the wine is in transit or even while the wine is being stored. Four of the more noticeable faults are described below; hopefully this gives you a head start on assessing wine and enhancing your overall dining experience.

Cork Taint

Wine drinkers and experts often talk about a wine being ‘corked.’ This is a very specific fungal fault that comes about when a residual fungus in cork reacts to chlorine that is used to bleach and sterilise the corks before they are used in the winery. Cork taint occurs in roughly 1 in every 20 bottles (5%) and leaves the wine smelling musty, like opening an old, empty cupboard; or like wet newspaper. It is a fault that is picked up by the nose immediately and does not usually require a sip for confirmation! A wine that is sealed with screwcaps, or with a glass cork can very rarely show evidence of this fault. This can be from wood chips used in the wine-making process.

Oxidation

Sometimes known as volatile acidity, this fault manifests itself in a number of ways on the nose and sometimes on the palate. At the simplest level, oxidation occurs when the wine has been exposed to oxygen when it should not have been. This can occur in the winery before preventative measure have been taken (such as the addition of sulphur), or can occur once the wine has been bottled, and is exposed to varying temperatures. Oxidised wine often looks dull in the glass, with a slight brownish tinge. This is considered a fault if the wine is very young. (Old wine naturally takes on a brownish colour). Red wine will look somewhat brick-red, and white wine will veer towards deep golden yellow. (Imagine what happens to an apple if you cut it and leave it exposed to air for half an hour or so). Oxidised wine can smell a bit like vinegar (acetic acid) or, in very bad cases, like nail varnish remover (ethyl acetate). Wine bottles stored in extremely hot environments often have corks which expand and contract with the temperature, allowing unwanted oxygen to enter the wine, leading to this oxidative character being present in the wine.

Reduction

There are various forms of reduction, but the most easily recognizable is Hydrogen Sulphide (H₂S). This is the ‘rotten egg’ gas and results from a reaction that occurs in the absence of oxygen, but in the presence of sulphur, either in the winery, but very commonly in the bottle. Sometimes, really badly reduced wine will smell like burnt rubber. In the case of H₂S, sometime decanting the wine, giving it a lot of air or swirling it quiet vigourously in the glass will get rid of the smell. There is also what is known as the ‘penny test’ where an old copper coin can be dropped into the glass. If the wine is only mildly faulty, the penny will lead to the wine’s aromas returning, and wine will be alright to drink.

Brettanomyces

Known as ‘Brett.’, this fault is considered benign by some wine tasters and sommeliers, particularly in the Old World. It is such a controversial ‘fault’ that many actually consider it a good thing, adding complexity to the aroma profile of a wine. However, Americans and Australians in general, consider this an all out fault. Brett occurs as result of a surface yeast (one that occurs on the surface of unclean barrels in the winery, for example) creating a strange-sounding chemical known as tetrahydropyridine. The resulting wine can smell a bit ‘horsey’ or like band-aids or overly ‘meaty’. If you find this character over-bearing and unpleasant, it is perfectly acceptable to ask for another bottle of the wine.

Additionally, look out for wines that smell ‘aldehyade-ic’ (like sherry) or like Geranium leaves, or overly garlicky or like old vegetables. This indicates faulty wine too.