How long should you rest coffee after roasting?

When you roast coffee, the heat in the drum incinerates some of the organic compounds of coffee seeds, a process that creates carbon gas. The same thing happens when you burn wood in a campfire, or toast bread in a toaster oven. This gas is most volatile right after roasting, but dissipates over time. We call this stage "off-gassing", and it's an important period of time for specialty coffee. Brewing too early, before coffee has a chance to off-gas, results in a sharp and often low-quality cup. 

Carbon gas acts as a barrier to extraction. Think of the gas forming a protective shield around coffee grounds, pushing away water and making it difficult to extract the flavors in your freshly roasted beans. So how much time do you really need to properly rest your coffee? The answer is a little more complicated than a simple number of hours or days. 

Extraction Matters

How you intend to extract your coffee will influence the amount of rest it requires. For evaluative cupping, we follow the SCA protocol and let coffees rest for 24-hours. This short off-gassing time leaves coffee tasting very fresh, but it's an important controlled variable for purchase cuppings.

Passive or low-pressure brew methods, like French Press, drip, or pour-over, need to rest for longer. Just two or three days is adequate to allow the gas to escape the beans, and you can brew a great-tasting cup of coffee. 

Higher-pressure brewing requires an even longer rest period. For espresso, we encourage customers to wait at least a week after the roast date before pulling shots on an espresso machine. Even longer may be better; I've found my "ideal" rest time frame to be about 15 days for espresso roasts. 

Impact on Flavor

What happens if you don't wait long enough? Brewing hyper-fresh coffee, roasted the same day or just one day ago, will make it hard to dial in your brew. All that trapped gas creates sharp flavors, which can produce metallic notes in your cup. Think of the flavor of pure carbonation, like when you open a soda water, and the first hit of air from the bottle hits your tongue. That flavor is sharp, gassy, and can taste a little like aluminum.

High amounts of residual carbon can also make your brew bed bubble into a frenzy, creating an uneven extraction and resulting in a fine layer of silt in the bottom of your cup. 

How to Rest

When it comes to resting your fresh-roasted coffee, don't overthink it. Coffee can rest in a food-safe bin or bucket for a day or two before packaging. If your bags have an off-gassing valve, you can bag your beans right away and allow the gas to escape through the valve. We don't recommend holding coffees until they're properly roasted. Instead, get them to your wholesale or retail customers as quickly as you can, and let them taste how that coffee improves with a few days of rest. 

You can also provide recommendations around rest times on your packaging, website, or social media pages. This is an opportunity for you to become the "subject matter expert" on your coffee. Letting people know when the coffee will be at its peak flavor ensures your customer has an even better experience with your product. 

Recommended Rest Times

Note: These guidelines apply to whole-bean coffee that's ground just before brewing. If you pre-grind your coffee for customers, rest times decrease dramatically. Ground coffee off-gasses at a much faster rate than whole bean.