Don't get me wrong, wine can turn bad or the environment of its presentation to you can turn it bad (my one encounter with returning a wine was due to the reside of lemon Joy I detected in my Syrah which the waiter confirmed). But what do we mean when we say a wine is bad? A bad wine is one that has been damaged or manufactured poorly (though these days with modern techniques this is rarely the case). In most circumstances a wine turns bad due to either improper bottling or, more often, improper storage. The three most common ways to recognize a truly bad wine are:
- The wine is "corked". This means that a fungus growing on the cork has come in contact with the wine. It has nothing to do with finding bits of cork in your glass which is perfectly harmless. Corked wine will have a musty aroma like wet cardboard. Corked wine is bad wine, send it back
- The wine is discolored. If a wine looks brown (especially a young wine), tastes flat or like cooked fruit and has a weak aroma the wine has been oxidized. Exposure to air ages wine and if the cork has dried out (say from storing it with the bottle standing up) it can shrink a little and allow air to enter the bottle and prematurely age the wine. Oxigenated wine is bad wine, send it back.
- The wine tastes like vinegar or tastes sour. This is due to a bacterial infection. Wine that needs penicillin is bad, send it back.
Some common things that make people think a wine is bad but doesn't affect the product are:
- Cork in the wine glass. This is actually pretty common particularly with older wines. If they bother you ask to have the cork removed. The waiter can decant your bottle if necessary but this is not the sign of a bad wine.
- Small white crystal are in the bottle/glass. Don't panic, this is simply precipitation of a chemical called tartaric acid in the wine and it is completely harmless. If you want, have the bottle decanted. The same goes for dark sediments that you can find in some red wines. Nothing to worry about, simply have it decanted.
- Mold on the cork. Sometimes in older wines you can find mold growing on the outside end of the cork. Don't worry, this often means that the humidity was a little high where the bottle was stored. Far more likely than not the wine is fine. Give it a taste to check but most likely it will be perfectly fine.
So there you have it, the basics of telling if a wine is "bad". Picking out a good wine is far more subjective. While there are certain things you would look for (balance between fruit, acid, alcohol and in red wines tannins, "complexity" of flavors and aromas, and "finish" or the length of time the experience lasts in your mouth), the basic rule of a good wine is do you like the taste? But more on this later.