🍷 Wine faults

Wine faults are unpleasant smells and tastes that arise from mistakes, microbes or poor storage. They differ from ordinary differences in taste: it is not a matter of preference but of spoilage.

The best-known faults are these. Cork taint is a musty or mouldy smell, caused mainly by trichloroanisole (TCA), which fungi in cork can form; even a few nanograms per litre can be noticed. Oxidation happens when too much air gets into the wine: it turns brown and loses freshness. Volatile acidity is mainly acetic acid, the acid of vinegar, and gives a vinegary smell; US rules, for example, cap it at 0.14 g per 100 ml in red wine and 0.12 g in other grape wine. Brett, or Brettanomyces, is a yeast whose volatile phenols give a barnyard or horsey smell. Reductive smells come from sulphur compounds such as hydrogen sulphide, often when the yeast lacks nitrogen.

Prevention matters most, because faults are hard to correct and the fix is never perfect. Winemakers care for yeast nutrition, limit oxygen access and use sulphur dioxide, the most common preservative against spoilage yeasts such as Brettanomyces. In some wines, such as sherry, Madeira or port, a higher level of oxidation is expected and valued, but in varietal and sparkling wines it is a fault.