We stored one bag four ways for four weeks

I ran the test because the same question comes up at the bar every week, and I wanted to answer it with numbers instead of habit. The coffee was our washed Huila, roasted on a Monday and split the next morning.

What makes coffee go stale

Four things age roasted coffee: air, light, heat and moisture, roughly in that order. Air does most of the damage. The aromas that make a cup taste of fruit are the first to leave, and once they are gone the coffee tastes flat and papery.

Grinding speeds all of it up. Ground coffee loses most of its aroma within a day, so the test used whole beans, ground fresh for each cup.

The results

Inés, Rui and I cupped the four portions side by side on day 28, without knowing which was which. Scores are out of 10, averaged across the three of us.

The freezer scored 8.0 and tasted almost like the day it was roasted. The original bag, with the air squeezed out and the zip closed every time, scored 7.5. The tin in the cupboard also scored 7.5. The glass jar on the open shelf scored 6.0, and all three of us called it dull before we knew what it was.

Light is the jar's problem. A clear jar on a sunny counter looks lovely and ages the beans faster than anything else in the test.

The gap between the bag and the freezer was smaller than I expected. If you drink a bag within a month and close it properly every morning, the bag it came in does nearly as well. Its one-way valve lets gas out without letting air in, which is why every bag we sell has one.

The freezer, done properly

Split the beans into portions of a few days each, in airtight bags or jars, before they go in. Take out one portion at a time and let it reach room temperature before you open it.

The mistake that ruins it is opening the bag cold. Water condenses on the beans straight away, and a portion that has thawed and gone back in tastes worse than one that never went in at all.

How much to buy

Filter coffee is at its best from about four days to four weeks after roasting. One person drinks about 250 g in a fortnight, which is why the subscription sends one bag every two weeks: it arrives a few days after roasting and runs out before it fades.

If that sounds right for your kitchen, try the subscription. We roast on Monday, post on Tuesday, and a bag costs 13.50 euros including postage anywhere in the EU.

Maksim, from the roaster