The case for resting coffee

Generally we recommend resting coffee for a few weeks at least.

Post roast, a coffee needs time to settle in. Very fresh coffee tastes sharp, intense and unbalanced. After a few weeks of rest, the individual flavors are more pronounced. The acidity and sweetness are better balanced. The complexity and clarity are higher.

How does flavor evolve throughout the aging process? We ran an experiment to find out. Spoiler: we find our coffees taste best between 4-8 weeks after roast.

Freshly roasted coffee typically tastes sharp and unbalanced. As the coffee rests, three things happen that help to balance and deepen the flavor.

Degassing

During roasting CO₂ is formed by reactions such as Maillard and caramelization. Around 5-10 mg CO₂/g will get trapped inside the bean structure. Post-roast, the CO₂ slowly diffuses out through the microscopic cracks formed during roasting.

Brewing fresh coffee with a high residual CO₂ leads to channeling. The CO₂ in the coffee bed blocks pore space (where gas sits, water cannot go), increases local pressure (gas expands and pushes against incoming water) and destabilizes the puck structure. As water chooses the path of least resistance, the flow channels, leading to uneven extraction.

Taste-wise this results in a sharp sourness and a hollow body (underextraction). The speed at which coffee degasses depends on how porous the coffee is. The more porous, the faster the CO₂ escapes. A darker roasted coffee is more porous and will degass faster. If you store coffee ground, the CO₂ will escape very quickly.

Moisture redistribution

Post roast, the remaining moisture in the bean is unevenly distributed. The outer layers are dry, the core is relatively wetter. This matters because it leads to an uneven particle size during grinding. The dry brittle exterior shatters easily, while the slightly wetter core fractures differently.

Uneven particle size means a less even extraction and less uniformity in your brews. Resting lets the moisture equalize, stabilizes the bean structure, improves the grind consistency and finally improves the extraction.

Chemical stabilization

A fresh roast contains harsh compounds such as sulfur, sharp acids and phenolics. These compounds are intense (taste-wise) but also highly volatile. They make very fresh coffee taste sharp, aggressively acidic and sometimes brothy.

Over time these volatiles dissipate and the coffee stabilizes thanks to a gentle oxidation. The flavors integrate and mellow.

Eventually though, the impact of time turns negative.

Oxidation creates cardboard like flavors. Complex aromatics break down. Brightness fades and nuance disappears.

Our optimal drinking window is 4-8 weeks post roast.

Frequently Asked Questions

We roast fresh batches every week. The coffee we ship is usually roasted the week before (maximum two weeks).

We roast relatively light, meaning the coffee is less porous so CO₂ escapes slower. Our coffee hence benefits from more rest compared to traditional roasters. The longer presence of CO₂ protects the bean from oxygen penetration, meaning the coffee stalls slower. Overall this increases the drinkable window of our coffees. In addition a convection-heavy system (like our Loring roaster), produces fewer smoky phenolics, less surface scorching and a cleaner sulfur profile. Meaning less harshness.

Natural coffees generally degass faster. They often have a higher sugar content and a lower density. More sugar means more CO₂ will form during roasting. Lower density will lead to larger pore network with more microfractures. Post roast, CO₂ will release faster and stabilize earlier for espresso.