How to tell when an aged beer has gone past its best

Every aged beer has a peak

Ageing is a slow change, not a slow improvement. A strong dark ale may get rounder and richer for a couple of years. Then the same chemistry that softened it keeps going and the beer starts to thin out. The trick is opening it near the top of that curve.

Fresh beers such as IPAs and pale lagers have their peak on the day they are packaged. For those, "aged" usually just means stale. This guide is mostly about beers built to keep: barley wines, quads, imperial stouts and sour beers.

Wet cardboard is the classic warning

The best-known staling note is wet cardboard or paper. It comes from oxidation. The compound most often linked with it is trans-2-nonenal. It shows up in almost every beer if you wait long enough. In a strong ale, a hint can sit behind the dried fruit without spoiling things. Once it is the first thing you smell, the beer is past its best.

Other oxidation notes are more mixed. Sherry, honey and toffee can be lovely in a barley wine. A thin, papery finish and a malt flavour that has gone flat and grainy are signs the decline has set in.

Reading the label before you open

Some warnings show before the cap comes off. Check the packaged-on date first. A best-before date alone tells you little about how old a strong ale is, since brewers set it differently. Our guide to packaged-on and best-before dates explains how to read both.

Look at the fill level in the neck. In a clear or brown bottle you can often see whether the level has dropped compared with a fresh bottle, which can mean a leaking seal. Check the cap for rust or a dark ring and the cork for dryness or crumbling. A label that is stained or faded hints at warm, damp or sunny storage.

None of these signs proves the beer is gone. Together they tell you to open it soon and taste carefully rather than putting it back for another year.

Signs in the glass and the bottle

• Flat beer. A tired seal can let carbon dioxide escape. The beer pours with no head and tastes dull.
• Gushing. A bottle that foams out the moment you open it, in a style that should not, often means a wild yeast or bacterial infection has kept fermenting.
• Haze and floating bits in a beer that was clear. Some sediment is normal in bottle-conditioned beer. Stringy or floating material is not.
• Faded colour or a dark ring at the neck. Can be a sign of long warm storage.

Off-flavours that mean it has turned

Some faults have nothing to do with gentle ageing:

• Vinegar sourness in a beer that was not meant to be sour points to acetic acid bacteria.
• Nail polish or solvent comes from ethyl acetate. Our guide to ethyl acetate explains how to separate it from fruity esters.
• Soy sauce or meaty notes can come from yeast breaking down after long, warm storage. Brewers call it autolysis.
• Musty, damp cellar aroma in a corked bottle can be cork taint.

Our guide to beer off-flavours covers the wider list.

Heat makes the decline faster

Brewers use a rough rule for staling: three days at about 32 °C does as much damage as thirty days at about 21 °C or three hundred days near 3 °C. The exact numbers vary by beer, but the direction never does. A bottle kept in a warm Indian cupboard can age as much in one summer as it would in several years in a cool cellar.

So when a beer has gone past its best earlier than expected, look at where it was stored before blaming the brewer. A car boot, a sunny shop window or a loft does more harm than time.

What to do with a bottle that has turned

Taste it carefully and take notes anyway. A faded beer teaches you what decline tastes like, which helps you catch the next one earlier. If it is merely tired, it can still go into a stew or a marinade. If it smells of vinegar, solvent or mould, pour it away.

Many people sense that something is wrong but cannot say what. Telling oxidation from infection, or autolysis from a dark malt note, takes trained comparison with known samples.

Your first step: next time you open an older bottle, smell it before tasting and write one word for the strongest aroma. If that word is "paper", open the rest of that beer soon.

Common questions

What does stale beer taste like?

Most commonly like wet cardboard or paper, from oxidation. Stale beer also tends to taste flat, thin and less bitter than it did fresh.

Why did my aged beer gush when I opened it?

Gushing in a style that should not foam over usually means wild yeast or bacteria kept fermenting in the bottle, raising the pressure.

Is sediment in an aged beer a bad sign?

Not on its own. Bottle-conditioned beers carry a layer of yeast. Stringy or floating material in a beer that was clear is more of a concern.