Canned beer does not spoil the way milk or meat does, but it does go stale, and cans have their own specific failure points that bottles do not. A can protects beer from light completely (bottles cannot do that even when brown), but it introduces a different set of risks: seam integrity, liner damage, and heat exposure during shipping and shelf storage. Here is what actually happens to beer in a can over time, and how to tell if one has genuinely gone bad rather than just gone flat or stale.
What Actually Degrades in a Can
A peer-reviewed sensory study on canned lagers (published in the Journal of the Institute of Brewing) tracked two canned lagers stored at 4, 12, 30 and 37 degrees C for up to 28 days, scoring tasters on staling attributes like cardboard, papery, honey and metallic notes. Staling correlated directly with both time and temperature: beer held at 37 C for a month tasted measurably more “cardboard” and “stale” than the same beer held cold, confirming what brewers have long assumed, heat is the main driver of canned-beer staling, not light (cans already block that entirely).
The two chemical processes doing the damage are oxidation (trace oxygen sealed in during canning slowly reacts with hop compounds and alcohols, producing that cardboard/papery flavor) and Maillard-type staling reactions that intensify with heat, turning fresh malt sweetness into a stale, sherry-like or honey note over time. Canning lines are actually very good at minimizing dissolved oxygen compared to older bottling methods, which is part of why fresh-focused breweries (most modern hazy IPA producers, for example) can almost exclusively in 4-packs now.
Signs a Canned Beer Has Gone Bad
| Sign | What it means |
|---|---|
| Dome or bulge on the top or bottom | Pressure buildup from an infection or a damaged seal, do not drink, this one is a genuine safety flag |
| Rust spots or pinholes on the can body | The liner or metal has been breached, air and contaminants can get in |
| Cardboard or wet-paper smell on opening | Oxidation from age or heat exposure, not dangerous but the beer is stale |
| Flat with almost no head at all | Lost carbonation, usually from age, heat, or a slow seam leak |
| Sour or vinegar smell in a beer that is not meant to be sour | Bacterial contamination, most likely from a damaged seal rather than normal aging |
A dented can is usually fine to drink as long as the dent has not stressed the seams (top and bottom rim) or created a pinhole. A dent in the flat side of the can body is cosmetic. A dent right on a seam is the one to actually worry about, since that is where the seal can fail.
How to Store Canned Beer Properly
Cold and dark, ideally under 12 C (54 F), which most home fridges easily beat. Standing upright is not required for cans the way it sometimes is for bottle-conditioned beers with yeast sediment, but keeping cans away from direct heat sources (a garage in summer, a car trunk, next to a stove) matters more than orientation. Most macro lagers and pale ales are brewed to hold up for 6 to 9 months from the can date even at room temperature, but hop-forward styles like IPA fade fast, the hop aroma compounds are the first thing to go, often within 90 to 120 days even under good storage.
For a deeper look at beer aging generally, including bottle-conditioned and cellar-aging styles, see our Can You Drink Expired Beer? guide, and if a beer has already lost its fizz specifically, our Is It Safe to Drink Flat Beer? piece covers that separately. If you are trying to keep a fridge full of cans consistently cold rather than guessing, our Best Beer Fridges and Kegerators guide compares real options by use case.
FAQs
Can canned beer actually go bad?
It does not spoil in a food-safety sense the way perishable food does, since alcohol and hop acids are naturally antimicrobial. What happens instead is staling, oxidation and heat exposure make it taste worse over time, and it can go genuinely unsafe only if the can itself is compromised (rust, pinholes, a bulging top).
How long does an unopened can of beer last?
Most standard lagers and ales hold up reasonably well for 6 to 9 months past the can date if stored cold. Hop-forward styles like IPA fade much faster, often within 90 to 120 days, since hop aroma compounds are the first thing to break down.
Does refrigerating canned beer make it last longer?
Yes, meaningfully. Sensory research on canned lagers found staling accelerated sharply at higher storage temperatures, so keeping cans consistently cold rather than at room temperature slows the cardboard/stale flavor development.
