DEGASING COFFEE – WHEN SHOULD WE EXTRACT THE COFFEE AFTER ROASTING ?

DEGASING COFFEE – WHEN SHOULD WE EXTRACT THE COFFEE AFTER ROASTING ?
Roast date ≠ drink date.
Here’s what’s actually happening inside the bean — and why it matters for your extraction.

The chemistry
Roasting triggers Maillard, Strecker & pyrolysis reactions (Clarke & Macrae, 1987; Wang & Lim, 2014) — generating massive amounts of CO₂. Over 80% of all gases formed during roasting are CO₂. Most stays trapped in the bean’s porous matrix after the drum.
Then the clock starts.

The degassing curve (Smrke et al., J. Agric. Food Chem., 2017)
→ ~40% of CO₂ exits in the first 24 hours → 50–70% gone by end of week 1 → degassing continues meaningfully for 3–4 weeks
But here’s the thing: CO₂ leaves much faster than your aromatics do. That gap is your flavour window.

Espresso vs. Filter — not the same rules
Espresso needs more rest. Pressure-based extraction magnifies CO₂ interference — excess gas causes channeling, flow restriction, and unstable, short-lived crema. (Wang & Lim, 2014; Smrke & Yeretzian, SCA 2019)
Rest time guidelines: → Light roast espresso: 10–14 days → Medium espresso: 7–10 days → Filter / pour-over: 3–7 days → Dark roast (any method): 2–5 days — but oxidation follows fast
Filter is more forgiving — the bloom handles much of the CO₂ release before extraction begins, and lower pressure means less disruption.

Temperature is the hidden variable (Smrke & Yeretzian, SCA Expo Lecture, 2019)
A +25°C increase in storage temperature = 100× faster freshness loss.
Freezing does the opposite: it slows degassing by ~12.5×, effectively extending your peak window from weeks to months — provided you use airtight packaging and avoid repeated freeze-thaw cycles.

Grind at the last possible moment
Studies show 40–73% of trapped CO₂ escapes within minutes of grinding (Wang & Lim, 2014; Shimoni & Labuza, 2000). The finer the grind, the faster it goes. Pre-ground coffee loses its gas — and its flavour — very quickly

The takeaway:
Fresh ≠ ready. Optimal ≠ day one. Your bag has a roast date. What it doesn’t tell you is the rest date. Learn your window. Brew in it