A recent thread on the Wine Berserkers forum – http://www.wineberserkers.com/forum/viewtopic.php?f=21&t=85187 – prompted me to write this post, which is likely experienced by many wine lovers around the world.
Many of us have dropped into a store or restaurant with wine in our car, perhaps forgetting how hot it can become, in a very short time, during the warm weather. This can also be an issue with wine deliveries, where often shipments are left by the carrier out in the sun. There are some indications to look for that will tell you that the wine was likely damaged and that you should *probably drink them soon.
Leakage at the capsule: this means the heat expanded the air inside the bottle (what little air is in a bottle), forcing liquid out. Now your wine has been exposed to oxygen, so you should probably think about drinking it sooner than later.
Bottle is hot to the touch: by ‘hot’, I mean truly hot, as if you heated it in the microwave for several minutes, and you can’t stand to hold it very long. This will have changed the molecular structure of the wine, cooking it slightly, so even if you instantly put it in an ice bath, the damage has been done. A slight warmth to the bottle is likely not worrisome, as the glass is relatively thick, and the liquid inside was probably somewhat cool at the time it hit your car, so if it is only a surface warmth, you are probably safe.
Cork popped off: this happens mostly to sparkling wine, as it is pressurized. (The inverse temperature will cause still wines to pop the cork, when they are frozen) Again, at this point, if you have any wine left in the bottle, enjoy it, probably right there in the car. On still wines, the thermal expansion of the liquid can generate a force great enough to push out the cork.
*Exceptions do exist, and the easiest way to determine if you might be safe is to determine what type of wine it was that was exposed. Many ‘big reds’ (Cabernet Sauvignon, Syrah, bold red blends) that are from recent vintages/current releases will probably be ok, as the wine itself is a bit more hearty. In many cases, it can IMPROVE the wine by giving it some accelerated aging 🙂