How Long Will Your Leftover Beer Last?

NEW YORK (MainStreet) – Maybe nobody came to your big St. Patrick’s Day party. Maybe they did show up, but everyone brought their own beer. Or maybe you simply overestimated how much beer you were going to need.

Either way, you woke up on Sunday to find a fridge still bursting with beer.

There are a few solutions to this problem (if you could really even call it that). You could start giving away six-packs to friends, family and random strangers, becoming the beer equivalent of the tooth fairy. You could throw another party.

Or you could simply drink it all yourself, which may be the easiest course of action. But how long do you have before it starts to go bad on you?

The answer to that question depends on a few factors, says Jeff Potter, a food science expert and author of Cooking for Geeks.

First, he notes that bottled beer lasts longer than draft beer found in a keg, on account of bottled (or canned) beer getting pasteurized first to cut down on bacteria. The beer in your keg will probably only be good for a month or two even if it’s kept cold, says Potter. As such, you might want to throw a second party fairly quickly to get rid of the extra beer.

If it’s bottled beer, then it depends largely on the alcohol content. Higher alcohol content obviously means a less hospitable environment for bacteria, so if your fridge is full of high-alcohol beers (those with an alcohol-by-volume north of 7%-8%), they will keep for a long time. Potter also notes that some people will even age their high-alcohol beers in the same way that they’d age a bottle of wine, sometimes for a year or more.

When it comes to St. Patrick’s Day parties, though, chances are you have mostly cheaper, lower-alcohol beers in the fridge – likely a mix of light beer and Guinness. These beers will probably keep for three to six months or so in the fridge, says Potter, who notes that it’s hard to pin down an exact time frame after which your beer will stop being drinkable.

That’s largely because beer doesn’t “spoil” in the sense of being rancid or unsafe for consumption. Rather, time simply changes the flavor in ways that you might not find pleasant.

“Beer, when it goes bad, isn’t going to hurt you, it just isn’t going to be enjoyable,” says Potter, explaining that the process of oxidization will change the beer’s flavors, rendering it “buttery” or “papery.” He adds that the process can even give “sherry-like” flavors to darker beer. These off-flavors will become more noticeable as time goes on, but you have at least a few months before you should start to notice any change.

Finally, a word on temperature. Your best bet is to keep the beer in the fridge – Potter says that as a general rule, the lower the alcohol content, the lower the storage temperature should be. But if you need to take some of the beer out so that you can put some actual food in the fridge, it’s not the end of the world. While most people will tell you that letting cold beer get warm will “skunk” the flavor, drinks columnist Lew Bryson says that a single instance of re-warming won’t have any appreciable effect on flavor. So don’t worry if you need to store some extra beer in the closet for a bit – just understand that the warmer temperatures may accelerate the timetable for how quickly you need to drink it.

Matt Brownell is a staff reporter for MainStreet. You can reach him by email at matthew.brownell@thestreet.com, or follow him on Twitter @Brownellorama.