Does Cold Beer Go Bad If It Warms Up?

There's a beer myth that just won't seem to go away. What's worse is that it could result in perfectly good beer being discarded, or at least regarded with some reluctance. The myth is that once cold beer warms up, that's it  — ruined — only good for trapping snails. This myth is likely a misunderstanding of how beer oxidizes over time. Don't get us wrong — keeping beer cold as much as possible is the best way to keep it tasting its best, but if your frosty brew doesn't stay ice-cold all the way home, all is not lost. If cold beer were ruined after warming up one time, there'd be hardly any good beer left in the world.

Beer degrades on a sliding scale, and the main villain that gains momentum as temperatures increase in pasteurized beer (most commercial beer) is the oxidation process. When beer oxidizes, it goes through a chemical process in which electrons play musical chairs across molecules, atoms, or ions, and this can be a result of oxygen or even trace metals in the beer, such as iron, copper, or manganese. The result is beer with a stale, muted flavor with notes like cardboard, paper, or even wine or sherry notes (not in a good way). Oxidization can also affect the volatile compounds in hop oils that contribute their tropical, piney, floral, or citrusy aroma and flavor, which is bad news for the fans of the many styles of IPA.

All beer has the potential to oxidize, but higher temperatures kick this process into higher gear exponentially. There is another axis on the graph of beer oxidation: Time. While it's true that beer stored at 90 degrees Fahrenheit will oxidize much faster than one stored between 50 and 60 degrees, oxidation doesn't happen instantly. Most beer is shelf-stable and can survive if left at room temperature (68-72 degrees) for as long as 120 days, thanks to pasteurization. Beer doesn't suddenly spoil on the 120th day, but slowly over time. All this is to say that if your cold beer gets up to room temperature for a short stint, it's not time to tip it down the drain.

Many craft beers from micro or macro breweries aren't pasteurized or filtered, which introduces a second enemy that gains traction at higher temperatures: Microbial growth or residual live yeast. Avoiding filtration and pasteurization preserves flavour in beer, making it preferable for craft breweries. The downside is that without pasteurization to kill off microbes or yeast cells that make it into the bottle, warmer temperatures can also contribute to these organisms proliferating and spoiling beer. Fear not — just as with pasteurized beer, craft beer isn't so fragile, and can survive a stint at warmer temperatures. Rapid, drastic, and frequent fluctuations in heat can boost oxidation and microbial growth, so avoid warming and cooling your beer (pasteurized or not) too often if you can help it.