My main question is really, I guess - how resilient is beer? I have some beer in my refrigerator that was cold when I bought it. I couldn't bring it home quickly due to having to visit my fiancee's grandmother in the hospital (short notice). It got pretty warm sitting out in the car and I have it refrigerated again. My roommate took one out to drink it, but fell asleep before he opened it - therefore, it got warm (room temperature) again. If I were to put it back in the refrigerator a third time, would the beer still be safe to drink? Would there be any quality loss?
There should be no reason why beer would lose any quality from being left out at room tempreture then being re-cooled.
During the brewing and distribution process beer is exposed to a wide range of tempretures numerious times.
Some specialst beers may include "adjuncts" or additional ingredients(fruit, honey etc...) that may be effect quality with a tempreture range (none spring to mind).However normal beer made with malt, hops & water should be fine.
Exposure to sunlight is more likely to affect beer than temperature.
It would be safe to drink, in the sense of it would not cause any harm to you.
Beer is very resistant to heat, it will preffer to be stored in a cold location, but will probably not go bad at room temperature for extended periods of time.
What really spoil it is is UV light.
But everything changes when the beer is opened, it should then be drinked on the spot, because it will soon loose all its CO2 and start oxidizing, making it terrible and probably hazardous.
Reaction to O2, full spectrum uv light, and cigarette butts from drunken friends would affect beer faster. Heat energy is produced by catalytic components at variable rates during the brewing process. The outcome is pretty stable. and delicious.