Is the Coffee Bean Degassing Period Really That Important? Does Degassing Greatly Affect Coffee Flavor?

"Coffee beans produce a large amount of gas after roasting, and these gases gradually escape from the coffee beans over time." Friends who frequently purchase coffee beans may have noticed that if the coffee package is about 1-2 days from the roasting date, it remains flat and deflated. If left unopened for 4-5 days, the coffee package becomes inflated and puffy - this is the coffee beans degassing.

Roasting dates from left to right: May 28th, 27th, 25th, 20th

What we refer to as the "resting period" is the process of using about a week's time to release a large amount of active carbon dioxide gas while retaining some gases to stabilize the coffee beans. So do freshly roasted coffee beans need to rest before they can be consumed? FrontStreet Coffee conducted two comparative experiments to see what differences exist.

Resting VS Not Resting

First, FrontStreet Coffee used Kenya AA coffee beans as representatives of medium-light roast, comparing brewing with coffee beans 7 days after roasting versus coffee beans 1 day after roasting.

Brewing Parameters

Coffee dose: 15g

Coffee-to-water ratio: 1:15

Grind size: 80% pass-through rate on #20 standard sieve (medium-fine grind)

Water temperature: 91°C

Dripper: V60#01

Rested Group

First, pour 30g of water and let it bloom for 30 seconds. During the blooming process, you can see the "coffee dome" rising rhythmically without large bubbles appearing. Then pour 100g of water in the second stage, and delicate coffee foam emerges. Finally, pour 95g of water in the last stage, wait until all the coffee liquid in the dripper has finished dripping, then remove the dripper to complete the extraction.

Not Rested Group

First, pour 30g of water and let it bloom for 30 seconds. Many large bubbles emerge during the pouring process. After completing the pour, one gas hole appears on the surface of the "coffee dome" continuously releasing large bubbles. Then pour 100g of water in the second stage - during the pouring process, large bubbles still emerge from the bottom, and the surface coffee foam is slightly coarse. Finally, pour 95g of water in the last stage, wait until all the coffee liquid in the dripper has finished dripping, then remove the dripper to complete the extraction.

Next, we brewed the medium-dark roast group, represented by Brazil Red Bourbon coffee beans. Again, we compared brewing with coffee beans 7 days after roasting versus coffee beans 1 day after roasting.

Brewing Parameters

Coffee dose: 15g

Coffee-to-water ratio: 1:15

Grind size: 75% pass-through rate on #20 standard sieve (medium grind)

Water temperature: 88°C

Dripper: V60#01

Rested Group

First, pour 30g of water and let it bloom for 30 seconds. The coffee grounds rise rhythmically during the blooming process, and due to the darker roast, the "dome shape" is even more beautiful. Then pour 100g of water in the second stage - dark brown coffee foam first emerges from the center, and by the end of the pour, the foam color turns golden yellow, with overall rich foam oils. Finally, pour 95g of water in the last stage, wait until all the coffee liquid in the dripper has finished dripping, then remove the dripper to complete the extraction.

Not Rested Group

First, pour 30g of water and let it bloom for 30 seconds. The coffee grounds expand rapidly upon contact with water, with large bubbles emerging during the process. During blooming, two gas holes appear on the surface of the "coffee dome" continuously releasing large bubbles. Then pour 100g of water in the second stage - when pouring begins, coffee foam emerges and quickly covers the surface. The surface coffee foam is slightly coarse but no large bubbles emerge. Finally, pour 95g of water in the last stage, wait until all the coffee liquid in the dripper has finished dripping, then remove the dripper to complete the extraction.

Results Comparison

During the brewing process, the differences between medium-light and medium-dark roast coffee beans with and without resting are very significant. When brewing unrested coffee, large amounts of gas emerge upon contact with water, increasing density differences within the coffee bed. Due to the harder bean structure of medium-light roast coffee, gases are not completely released during the 30-second blooming time, so large bubbles appear during the second pour. Coffee beans that have gone through the resting period are much more stable during brewing.

Let's also distinguish how much difference exists in flavor between rested and unrested coffee. Through comparing the two groups of coffee, there is no significant difference in taste. However, in terms of aroma, the rested coffee is more fragrant. After tasting the unrested group, a dry sensation appears in the throat, creating a "harsh feeling." This is also because coffee beans that cool down rapidly after high-temperature roasting tend to develop a "fiery heat" sensation, while the resting period helps stabilize the coffee beans and reduce this "harsh feeling."

In conclusion, FrontStreet Coffee still recommends that when you first get freshly roasted coffee beans, don't rush to try them immediately. Let them rest for about a week before tasting. The resting period is indeed necessary.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473