I received a two-part foodie question the other day. “Is the beer that I leave on a shelf in my garage losing quality? How long can beer be safely stored?” My answer: A handful of factors influence overall quality of beer, but the product is most susceptible to air and light.
It’s not likely that the beer will be exposed to air in the garage. Many beers are produced with a little extra CO2, which eliminates residual oxygen in the beer and prevents stunted shelf life. Additionally, aluminum cans are tightly sealed, and bottles now use specially designed caps to lock out oxygen. Since you’re probably not cracking open a beer with the intent of drinking it days/weeks later, there’s little risk for great flavor degradation here.
It’s much more likely that beer in the garage will experience quality loss from light exposure. Light causes a “skunky” flavor to develop in beer, created by MBT (3-Methyl-2-butene-1-thiol, if you aim to impress). This is why we find beer in cans or dark bottles with opaque secondary packaging; producers are shielding their product from a chemical reaction initiated with light exposure, sometimes referred to as photodegradation. The mechanism for this reaction wasn’t widely understood until after 2001, when (then) new research emerged. After ’01, we understood that hops (an ingredient which imparts beer’s characteristic bitter flavor, aroma, and a bit of product stability) contains compounds called isohumulones that degrade with light, break down into free radicals, and react with sulfur-containing compounds… yielding a flavor reminiscent of a skunk smell. More recently, we’ve learned that riboflavin (which we know to be present in beer) catalyses the reaction. Long story short, don’t expose your beer to sunshine!
For the answer to part two of the question, I consulted a few familiar beer companies – Samuel Adams, MillerCoors, Anheuser-Busch, and Heineken. All recommend consumers check the best-used-by date printed on the bottle to be certain the freshest taste is enjoyed. According to the MillerCoors site, shelf life is 17-26 weeks for their domestic offerings, and longer for imported (based on ship time required for import). Anheuser-Busch claims the freshest taste of their products is within 110 days of the “born on date” they mark on the bottle. Heineken recommends their products be “stored in a cool, dry place out of direct light and heat.” And, Sam Adams recommends “No one should drink old beer” … I have to agree.
A Food Science tid-bite: …because I know some of you are making mental note of several beers in clear bottles (Miller Genuine Draft, Corona, etc.) and those in green bottles (several imports, including Heineken)… Since we know light easily passes through clear/green glass, why would those bottles still be on shelf? Some beers bottled in clear glass contain no hops, or use a modified hops, which produce no MBT – fascinating advancements. And Corona? They address some of the off flavor with clever marketing – most of us pop a lime slice into those bottles, right? (More later if you’re interested.) As for the green bottles…honestly, most of the US market has grown to accept the “skunkiness” as a characteristic component in the flavor profile. Although, rumor has it that a few green-bottle companies have researched how to remove riboflavin from beer, thereby reducing/removing the unpleasant flavor.