Common wine faults, for quality and supply teams

Fault or just not to my taste?

The first job is to separate genuine faults from complaints about style. A tannic red, a very dry white or a wine with a savoury, earthy note may simply not suit the customer. A fault is something that should not be there in any version of the wine.

Some things look alarming but are harmless. Small crystals in a white wine or on the cork are tartrates, sometimes called wine diamonds, which form when wine gets cold. Sediment in an older red is normal. Neither is a fault. Both are worth explaining kindly to the customer, ideally with a short note the sales team can reuse, because the same question will come back every winter.

Cork taint

What it smells like. Musty, like a damp cellar, wet cardboard or a wet dog. At low levels it simply mutes the fruit, so the wine seems dull rather than obviously faulty.

Where it comes from. A compound called TCA (2,4,6-trichloroanisole), usually from natural cork, occasionally from contaminated winery materials such as wooden pallets or cleaning products. It is introduced before the bottle leaves the winery or at the cork supplier, not in transit.

Who owns it. The winery and its cork supplier. A pattern across one batch or supplier lot is worth escalating. Screwcaps and some technical corks remove the risk from the closure.

Oxidation and heat damage

What it looks and tastes like. Whites turn deep gold or brown. Reds turn brick or orange early. Fruit fades and is replaced by bruised apple, nutty or sherry-like notes. Heat-damaged wine tastes flat, jammy or stewed. The cork may be pushed up or leaking.

Where it comes from. Too much oxygen at the winery or through a faulty closure, or heat in storage and transport, which speeds everything up. In India this is the fault most often caused after the wine has left the winery. Our guide to wine storage and the cold chain covers prevention.

Who owns it. Often the supply chain. Tracking complaints by route, warehouse and season usually shows where.

Volatile acidity

What it smells like. Vinegar, or a solvent smell like nail polish remover.

Where it comes from. Acetic acid bacteria and some yeasts, working when wine is exposed to air, for example in barrels that were not kept topped up. A trace adds lift to some styles. Too much is a fault. Many countries set legal limits on volatile acidity.

Who owns it. The winery, specifically cellar hygiene and how well vessels are kept full.

Reduction, Brett and refermentation

Reduction. Rotten egg, struck match, cooked cabbage or rubber. Caused by sulphur compounds formed when yeast is stressed or wine is kept too far from oxygen. Mild cases sometimes ease with air in the glass.

Brettanomyces. A spoilage yeast that gives barnyard, sticking plaster or smoky, medicinal notes, mostly in reds. Some drinkers tolerate a trace. At higher levels it flattens the fruit. It lives in poorly sanitised barrels and cellars.

Refermentation. A still wine that fizzes, or looks hazy, has started fermenting again in the bottle because yeast or bacteria survived alongside leftover sugar. It points to a stabilisation or filtration problem at bottling.

Light strike. White and sparkling wines in clear glass can develop cooked cabbage or wet wool notes after exposure to light, including bright shop lighting.

A complaint process that finds causes

• Taste the returned bottle and a retained sample from the same lot, if you keep them. Lot codes on the bottle make this possible.
• Name the fault in plain words and record it consistently.
• Log complaints by lot, route, distributor, region and month.
• Send winery-origin faults, such as cork taint, volatile acidity and Brett, back to the winemaker. Send storage faults, such as heat damage and light strike, to the supply team.

The hard part is getting everyone to name faults the same way. A team that has smelled cork taint and oxidation side by side, in a controlled session with spit cups, will log complaints far more reliably than one working from a list of words.