Coffee beans with a printed roast date

Two dates appear on coffee bags and only one is useful. A roast date says when the coffee was roasted, which lets you work out how old it is. A best-before says when the seller stops standing behind it, which is usually twelve months out and tells you nothing about whether it is any good now.

Why the distinction matters

Coffee does not spoil. It goes flat. Carbon dioxide escapes over days, the aromatics fade over weeks, and the oils eventually oxidise. A bag with a best-before ten months away might have been roasted last week or last spring, and there is no way to tell from the packaging. Printing a roast date is a roaster choosing to be checkable, which is why it correlates so strongly with everything else being published.

How old is too old

Coffee needs a few days to degas before it brews well, so the day after roasting is not the target. The usable window is roughly two to six weeks for filter, a little longer for darker roasts already past their most aromatic phase. Beyond that it does not become dangerous, it becomes dull, and the first thing to go is exactly what you paid extra for on a single-origin bag.

It matters most at the light end

A light roast has more delicate aromatics to lose and fewer bitter ones to hide the loss behind, so staleness is obvious. A dark-roasted bean stales faster in one sense, because its surface oils are exposed to air, but it starts from a flavour that is less about aromatics in the first place. Storing coffee beans properly covers what actually ruins them, which is air and heat rather than the freezer everyone worries about.

What to do with this list

Treat a printed roast date as a signal about the roaster as much as about the bag. The ones who print it tend also to name the farm, the process and the altitude. Buy smaller quantities more often, and prefer a roaster who ships soon after roasting over one who holds stock.