The Roast Date, and Why We Read It First

When we open a new bag, the first thing we look for is not the tasting notes. It is not the origin, or the process, or the variety. It is a date.

Roasted coffee has a shelf life measured in weeks, not months. A bag with no roast date is a bag telling you something about how much its seller cared, and it is almost never good news.

The window

Fresh-roasted coffee off-gasses carbon dioxide for the first several days after it comes off the roaster. Brew it too soon — day one, day two — and the bloom will erupt through your filter and the extraction will be uneven and gassy. Wait too long, and the volatile aromatics that gave the coffee its shape will have drifted out of the bag entirely.

The rough window most roasters aim for is somewhere between five and thirty days off roast. Espresso tends to like the later end of that window; filter tends to open up earlier. There are exceptions in both directions, and some roasts are engineered to peak later. But if you are brewing coffee that was roasted the same week you bought it, you are probably early. If you are brewing coffee that was roasted three months ago and vacuum-sealed in a supermarket bag, you are almost certainly late.

What you can taste

Stale coffee is not offensive in the way that spoiled food is offensive. It is duller. Flatter. The bright acidity — the thing that would have made a Kenyan cup snap on your tongue — has softened into cardboard. The aromatics that would have carried strawberry, or bergamot, or dried fig, have gone quiet. What is left is body and bitterness and a faint, papery reminder of what the coffee used to be.

The frustrating thing is that most of us have been drinking coffee like this for our whole lives, and we do not know what we are missing until we drink a cup that is not like this. Which is why the roast date matters more than any single origin or process detail. A fresh bag of pleasant, ordinary coffee will outperform a stale bag of extraordinary coffee, every time.

Reading the bag

A good specialty roaster prints the roast date on the bag or the label. Not a “best by” date, which is roughly meaningless. A roast date. Sometimes it is stamped, sometimes it is written by hand, sometimes it is on a small sticker on the back. Read it. If you cannot find one, that is a data point in itself.

Also worth reading: a decent bag will have a one-way valve — the little rubber disc that lets CO2 escape without letting air back in. That is not decoration. It is what keeps the coffee from oxidising itself into cardboard before you open it.

A rule of thumb

If a bag is more than six weeks off roast when you open it, we treat it as a cooking coffee — fine for the pot in the office, not the pot we brew when someone is paying attention. If it is more than three months off roast, we do not brew it at all. It will not be dangerous. It will just be sad.

Buy less coffee, more often. Two 250g bags a month, alternating, will teach you more about your palate than a single kilogram bag bought in bulk and slowly forgotten.