Freshness, Degassing and Storage

Roasted coffee is not shelf-stable in any meaningful sense. It is a dry, porous solid full of volatile aromatics and trapped carbon dioxide, and it starts changing the moment it leaves the roaster.

Degassing

Roasting produces CO₂ — several litres per kilogram — that stays trapped in the cellular structure. It escapes over the following weeks, fastest at first. In the cup, trapped CO₂:

• repels water and causes uneven wetting (the dramatic bloom on very fresh coffee is exactly this);
• suppresses extraction, making very fresh coffee taste flat, thin and sometimes sour;
• in espresso, produces excessive crema, channelling, and shots that change day to day.

Rough resting windows, measured from the roast date:

	Filter	Espresso
Light roast	7–21 days	14–35 days
Medium roast	5–14 days	10–28 days
Dark roast	3–10 days	7–21 days

Dark roasts are more porous and degas faster; light roasts hold onto gas longer.

Staling

After degassing, the enemy is oxidation and the loss of volatiles. Aromatics evaporate, lipids oxidise, and the cup loses brightness and complexity, sliding toward flat, papery, and eventually rancid. Warmth, oxygen, humidity and light all accelerate it. Whole beans at room temperature are usually noticeably diminished by six to eight weeks and clearly stale by three months.

Ground coffee stales far faster — a thousandfold more surface area exposed to air. Most of the aromatics are gone within an hour of grinding. Grind immediately before brewing; it is the single biggest freshness win.

Storage

• Original bag with a one-way valve, sealed, in a cupboard: fine for the first few weeks.
• Airtight, opaque container: a small improvement; less headspace is better, so a container the coffee nearly fills beats a large one.
• Vacuum canisters: helpful for slowing oxidation; they don't stop degassing.
• Fridge: don't. Condensation and absorbed odours.
• Freezer: yes, done properly. Freezing at −18 °C or below nearly halts staling. Portion into airtight containers (small jars, vacuum bags) so you never re-freeze a thawed batch, and grind straight from frozen — frozen beans grind slightly finer and more evenly, so adjust a step coarser.

Freezing single doses in small tubes has become standard in competition and café practice. A coffee frozen at its peak can be brewed months later with little loss.

Practical timeline

1. Day 0–3: heavy CO₂. Brew if you must, expect it to be off.
2. Day 5–21: the window. Filter coffee peaks early in it, espresso later.
3. Week 3–6: gradual decline; still good, especially for immersion and milk drinks.
4. Week 6+: freeze anything you haven't opened; use up what you have.

A "best before" date twelve months out is a food-labelling convention, not a description of when the coffee will taste good. Look for the roast date.