A
wine fault or
defect is an unpleasant characteristic of a
wine often resulting from poor
winemaking practices or
storage conditions, and leading to
wine spoilage. Many of the compounds that cause wine faults are already naturally present in wine but at insufficient concentrations to adversely affect it. In fact, depending on
perception, these concentrations may impart positive characters to the wine. However, when the concentration of these compounds greatly exceeds the
sensory threshold, they replace or obscure the
flavors and
aromas that the wine should be expressing (or that the winemaker wants the wine to express). Ultimately the quality of the wine is reduced, making it less appealing and sometimes undrinkable.