Resting Roasts: Is Fresher Better?

By Scott Rao

Republished by ST. DION Coffee with permission.

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From ST. DION

At ST. DION, we believe coffee reaches its full potential when every stage—from sourcing to roasting to brewing—is approached with intention. In this article, Scott Rao explores why “freshly roasted” doesn’t always mean “best tasting,” and how resting coffee can unlock greater sweetness, clarity, and balance.

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Resting Roasts: Is Fresher Better?

“Resting” coffee after roasting is a hot topic, and apparently a confusing one at that. Around the time the Loring became popular and more third-wave roasters began roasting ultra-light, or “Nordic style,” it became common for roasters to recommend resting beans for weeks or months after roasting. That was a revolutionary change from traditional practices.

Why We Rest Coffee for Espresso

Historically, most roasters and baristas were on the same page when it came to resting beans to be pulled as espresso. Pulling shots of coffee roasted recently and ground on demand results in massive amounts of crema and lower extractions than shots pulled from beans several weeks off roast.

The reason for this is likely that the back pressure caused by degassing during espresso extraction forces the barista to use a coarser grind with very fresh coffee, and/or the outgassing may make it more difficult for the water to rapidly dissolve solids from intact cells within the grounds. (In a pressurized espresso basket, there is nowhere for the gas to escape to; in filter brewing, gas released when water wets the grounds escapes into the atmosphere and does not provide meaningful back pressure.)

Until the last several years, common practice was to rest espresso beans, but not beans for filter coffee. More recently, especially as the popularity of the Loring has exploded and more roasters have chosen to roast ultra-light, resting has become a standard, almost universal practice.

Why Would We Rest Beans for Filter Coffee?

There seems to be a connection between the strength of a bean’s cellulose structure and the need to rest coffee. Lighter roasts have stronger, less brittle, less porous cell structures.

I am not sure if anyone knows exactly what changes during resting—whether the cellulose weakens with time or, more likely, slow chemical changes affect coffee flavor in a way that makes the coffee seem more developed. Most of us would agree that the lighter the roast, the more resting is required to reach the coffee’s flavor peak.

What Factors Make Resting Beneficial?

As noted, light roasts seem to benefit more from resting.

Coffee from air roasters also seems to benefit more than coffee from drum roasters. Presumably, the conductive heat transfer in drum roasters damages the outer layers of the beans during roasting, weakening the cell structures, making them more porous, more developed, and therefore less in need of resting.

Resting Times Among Different Air Roasters

I have spent the last several months roasting on two air roasters: a Roest sample roaster and a 15 kg IMF. I roast on the light side by almost any standard, and my coffees seem to benefit from some rest. However, while they may peak one or two weeks after roasting (the jury is still out), they taste perfectly fine a day or two after roasting.

Not all air roasters are the same. In my experience, coffee from Loring machines requires longer resting periods than coffee from other air roasters.

I’m not sure why that is, but one of two unique features of the Loring is likely responsible: the roasting chamber is pressurized, and the roasting environment is oxygen-free (according to Loring). One of those two factors is probably why coffee from Lorings requires longer resting times.

How Long Should You Rest Coffee?

Judging by my inbox, many people assume all roasted coffee needs lengthy resting periods.

Of course, everyone has his or her own preference.

I would argue that the optimal resting period depends on roast level, whether the coffee came from a drum or air roaster, and, if it came from an air roaster, whether that machine was a Loring.

If I were forced to drink a dark, oily roast, I would not rest it for more than a day, as it would likely begin tasting rancid within a few days. (And of course, I would add salt—haha.)

I don’t find coffee from classic drum roasters benefits from more than a day or two of rest unless the coffee is underdeveloped.

As for air-roasted coffee, I would probably rest it anywhere from one to four weeks, depending on its development level and whether it came from a Loring.

Storage Conditions and Resting

Storage plays a major role in how coffee evolves during resting.

Freezing vacuum-sealed coffee slows the aging process so dramatically that it may take months or years to reach the same condition as coffee rested for one or two weeks at room temperature.

Likewise, pressurized cans, such as those used by Illy, significantly slow aging. Coffee stored in cooler environments develops more slowly, while warmer storage accelerates degradation.

The Bottom Line

There is no one-size-fits-all resting period.

Consider the roasting machine, roast level, degree of development, and storage conditions when deciding when a coffee has reached its peak.

Comments welcome.

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About Scott Rao

Scott Rao is one of the specialty coffee industry’s leading authors, educators, and consultants. 

Originally written by Scott Rao. Republished by ST. DION Coffee with permission.