There are some simple ways to tell that your wine, opened or unopened, has gone bad. The following signs are all reasons you should promptly discard that bottle of wine and reach for something else to serve:
The wine tastes carbonated, even though it’s not meant to be a sparkling wine
Wine tastes sweet when its flavor notes are not meant to be sweet. Red wine is something to especially be wary of tasting sweet.
The cork isn’t firmly in place–and it may not have just been an error on your part. While a slightly loose cork doesn’t always spell for disaster if used very quickly, you should proceed with caution. One tell-tale sign is a cork that is ever so slightly pushed away from the bottle, which could be a sign of the cork itself reacting to the wine both expanding and overheating.
A brownish or yellow hue, both signs the wine has oxidized.
An unpleasant aroma. Don’t play games with this one–anything that smells moldy, like vinegar, or even resembles the smell of raisins is a bad sign.
Chemical taste. If there is an odd taste that reminds you of chemicals, get rid of the bottle.
What’s the proper way to store wine so I make sure it doesn’t go bad?
We’ve already touched on this a little, but this point deserves some emphasis. Properly storing wine, both opened and unopened, can ensure you won’t embarrass yourself, or even make you and others sick when entertaining.
For unopened, tightly sealed bottles:
Store in a cool, moist place, preferably on a wine rack
Store the bottles sideways, as opposed to standing
Keep it in a dark place with as limited light as possible, to protect against UV rays
For opened bottles:
While this applies for both, make sure temperature stays consistent, as greater changes excel a wine’s expiration
Keep the wine refrigerated
Humidity should be around seventy percent
Make sure the cork is as tightly secured as possible