Roasting traps carbon dioxide inside the bean. Over the following weeks that CO₂ escapes, taking volatile aromatics with it. Freshness is really a curve: too early and the gas disrupts extraction, too late and the aroma is simply gone.
The curve, week by week
- Days 0–3: heavy degassing. Pour-over blooms violently and espresso gushes. Usable, rarely optimal.
- Days 4–14: an illustrative filter tasting interval, not a universal peak. Aromatics are intact and the gas has settled.
- Days 10–21: an illustrative espresso comparison interval. Slightly longer rest gives steadier flow and more sweetness.
- Weeks 4–6: still perfectly pleasant, gradually flatter and more one-dimensional.
- Beyond 8 weeks: assess aroma and storage; a date alone cannot establish flavour or safety.
Darker roasts are more porous, degas faster and go stale sooner than light roasts.
What actually kills coffee
Oxygen first, then heat, moisture and light. Grinding accelerates everything: ground coffee has more exposed surface and its aroma changes after grinding; there is no universal minute at which most aroma is lost. That single fact is why a grinder outranks almost every other purchase.
Storage that works
- Keep beans whole until the moment you brew.
- Use an opaque, airtight container — a one-way valve bag is fine if you press the air out.
- Store in a cool, dark cupboard, never on top of the machine or next to the hob.
- Buy in quantities you will finish in three to four weeks.
The freezer question
Freezing works, with rules. Portion beans into small airtight bags, freeze once, and never refreeze. Brew straight from frozen or let the sealed bag reach room temperature before opening — to limit condensation on the beans. Packaging and storage history affect the outcome. For a bag you cannot finish in a month, the freezer beats the cupboard by a wide margin.
Build a useful tasting log
Choose two tasting dates for the same bag rather than treating the planner’s date as a deadline. Record roast date, opening date, storage, dose, ratio and one aroma or taste observation. Hold the recipe constant on the second date. If the cup changes, decide whether you prefer it before altering the grinder. The calendar is a reminder for this comparison, not evidence that a particular bean peaks on a specific day.
References and scope
Reviewed November 5, 2026. References support the named background topics; the comparison plans and arithmetic above are illustrative, not claimed equipment tests. Follow the instructions for your own equipment.