The most common crystals found in wine are tartrate crystals (specifically potassium hydrogen tartrate - shown here), and these are often found adherent to the underside of the cork, or in free suspension. Wines that have been cold stabilised by the winemaker have been chilled in order to bring these crystals out of solution so that they may be removed. If this is not done, they may form later in the bottle, especially if kept in a cold cellar. They are of no concern, although they are again unpleasant if taken into the mouth, particularly if large when they may be mistaken for shards of glass.
When we refer to corked wine we are talking about wine which is spoiled because a kind of mould infects the cork and then is transferred into the wine. It's worth remembering that cork is a natural product which comes from the cork tree so this mould is a naturally occurring thing. The mould produces a compound called trichloroanisole (TCA). A "corked" wine has distinctive and unpleasant smell which is unmistakeable. Depending upon how badly infected the wine is, it will quite literally smell mouldy or musty or smell of damp cardboard. However, a lot of people drink a corked wine and just think that the wine is poor, not realising that it is, in fact, faulty. If a wine doesn't smell fresh and fruity and taste as it should then replace it for the customer.
Heat damaged wines are often casually referred to as cooked, which suggests how heat can affect a wine. The ideal storage temperature for wine is generally accepted to be around 13°C (55°F). Wines that are stored at temperatures greatly higher than this will experience an increased aging rate. Wines exposed to extreme temperatures may even push up between the cork and bottle and leak from the top. When opening a bottle of wine, if a track of wine is visible along the length of the cork, the cork is partially pushed out of the bottle, or wine is visible on the top of the cork while it is still in the bottle, it has most likely been heat damaged. Heat damaged wines often become oxidized, and red wines may take on a brick color.
What happens to wine when it has been exposed to oxygen. It makes the wine taste flat and dull, if not downright unpleasant and it also changes the colour to make it darker. Some wines are purposefully oxydised, for example Sherry but generally oxydised wine is not a good thing.
Sedimentation within the bottle is a natural occurrence in many wines, generally those designed to withstand some ageing, and it simply reflects the solid matter settling out of the wine. If poured into the glass it can be pretty unpleasant, and if this were to happen in a restaurant it would certainly be a cause for complaint. The wine should have been decanted.
Sulfur is used as an additive throughout the winemaking process, primarily to stop oxidation as mentioned above. When managed properly in wine, its presence there is often undetected, however when used recklessly it can contribute to flavour and aroma taints which are very volatile and potent
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