The Maderization Process

• The effects of heat on wine are well-documented enough that the heat-spoiling process has a name of its own: maderization. Maderization is when exposure to heat affects a wine's coloring and flavor, typically giving it a distinctly sweeter taste. The wine's flavor profile starts to take on the taste of fruits and nuts, and white wines may start to take on a brownish hue. In sweeter wines and dessert wines, these changes to the flavor and mouthfeel may be subtle -- in dry reds, on the other hand, they can easily compromise the wines' unique qualities.

Signs of Spoiling

• In addition to the noticeable flavor changes, wine that has been spoiled by heat exposure is identifiable before even opening the bottle. While color changes are more noticeable in whites than in reds, wines that have been heat damaged expand in the bottle, forcing the cork upward in the bottleneck. If your wine's cork has started to emerge from the mouth of the bottle, this is a sign that the wine inside has been at least partially spoiled by the heat. The cork's movement may have also allowed air into the bottle, which hastens the spoiling process significantly -- air entering the bottle makes the wine start to oxidize, which limits its ideal shelf life to only a few days, at best.

Heat Time Limits

• Wine should be kept at a consistent and mild temperature, and sitting in the heat for as long as five hours -- or even less -- can cause it to spoil. No matter its color or type, your wine should never be held at a temperature of 86 degrees Fahrenheit or higher, and can only be kept between 76 and 85 F for 30 minutes or less. At 75 F or below, it can last as long as one to four weeks, but for periods longer than that, it should remain at a temperature between 50 and 60 F. Failure to follow these guidelines will change the composition of your wine, so be mindful of your environment -- leaving a bottle in a hot car for even 30 minutes or less can spoil it.

Temperature After Opening

• After opening a bottle of red or white wine, it should be corked and refrigerated. Even after being recorked, the bottle has oxygen inside, which actively compromises the wine's flavor. While refrigeration slows down this process, it does not stop it altogether, and you shouldn't save wine for more than three days or so -- after that, the oxidation process has significantly changed its taste. Red wine can sit out for as long as it takes to warm back up to ideal serving temperature -- between 60 and 65 F -- but should be returned to the refrigerator as soon as you're done with it.