Why is Blooming Necessary in Pour-Over Coffee? Why Does the Water for Degassing Use Double the Amount of Coffee? What Determines Coffee Concentration?

The Blooming Question: Should You Remove Coffee Liquid During the Bloom Stage?

Today, FrontStreet Coffee discovered an intriguing topic from the past that we'd like to share with everyone: "Does pour-over coffee taste better when you remove the coffee liquid during the blooming stage?" The reason behind this question is equally fascinating, so let FrontStreet Coffee explain~

As we all know, the purpose of blooming in pour-over coffee is to wet the coffee grounds and release carbon dioxide that hinders extraction, creating an optimal environment for subsequent hot water extraction to better extract flavor compounds from the coffee grounds. This means we need to reserve more hot water for the main extraction stage after blooming, allowing it to maximize its value. Therefore, we should limit the amount of hot water used during the blooming stage – as little as possible.

Conveniently, dry coffee grounds need to absorb hot water to become saturated. According to experimental statistics, coffee grounds need to absorb approximately twice their weight in hot water. Therefore, the hot water used during blooming is set to twice the amount of coffee grounds. This approach allows the grounds to bloom while becoming saturated, without "wasting" excessive hot water. However, not all of this hot water will be completely absorbed by the coffee grounds. This is partly due to uneven distribution of hot water, which cannot reach every coffee particle uniformly; additionally, the pour rate and grind size directly determine the penetration speed of hot water, indirectly affecting the absorption by coffee grounds. Therefore, when we pour hot water, not all of it will be completely absorbed – some will permeate through to the bottom chamber.

Then, some people speculated: since this portion of hot water serves to wet the coffee grounds and remove extraction obstacles, doesn't this mean their extraction environment is weaker than that of subsequently poured hot water? Wouldn't the concentration of the permeated coffee liquid be lower? If we remove it, could we avoid it diluting the concentration of the entire cup of coffee?

Should Blooming Liquid Be Removed?

Have you noticed that this practice is remarkably similar to flow separation? Flow separation refers to cutting off the coffee liquid from the final extraction stage because it might contain excessive undesirable flavors, thereby preventing obvious negative tastes in the coffee. The reason for removing blooming liquid, however, is to avoid it diluting the concentration of the entire cup of coffee. If both techniques were applied to the same brew, it would be what we call "removing both head and tail."

Regarding flow separation, FrontStreet Coffee has shared detailed information previously. If interested, you can refer to "Is Flow Separation Necessary in Pour-Over Coffee?" The general idea is that flow separation is feasible but shouldn't be used indiscriminately. However, regarding "removing the head" – that is, removing the coffee liquid that permeates during blooming (too long, let's call it "blooming liquid" hereafter) – FrontStreet Coffee can definitively state that this is not feasible! Why? Let FrontStreet Coffee brew a cup to explain~

For this brewing, FrontStreet Coffee used Panama Green Label Geisha beans. Because of its medium-light roast, it has moderate water absorption speed, and some coffee liquid will inevitably permeate during blooming. Additionally, its prominent flavors help us more directly compare the difference between removing and not removing the blooming liquid. The extraction parameters are as follows: 15g coffee grounds; 1:15 coffee-to-water ratio; grind setting at 10 on Ek43 (similar to fine sugar, with 80% passing through a #20 sieve); water temperature at 92°C; V60 dripper; brewing method remains three-stage infusion.

Let's begin with blooming, using twice the amount of coffee grounds in water (30ml) for a 30-second bloom! FrontStreet Coffee finished pouring 30ml of hot water in 8 seconds, and by the 10-second mark, coffee liquid began to permeate!

By 24 seconds, the coffee liquid stopped permeating. At this point, we poured the liquid in the server into a small cup for later use.

Then we reset the weight to zero and restarted our extraction (this makes calculation easier)! In the second stage, we poured 130ml of hot water using a small circular motion with a large circle. When the water level dropped to nearly exposing the grounds, we poured the remaining 65ml of hot water using a large circular motion with a small circle. After extraction was complete, we could begin our comparison!

Actually, we can directly see the answer to this question from the picture below, because the blooming liquid is very dark in color, indicating it has a high concentration. However, for better verification, we must follow all necessary procedures~

Comparison Results

Through testing with a coffee concentration refractometer, we found that the coffee without blooming liquid had a concentration of 1.25%. In terms of flavor, it exhibited subtle jasmine floral notes, high sweetness reminiscent of honeydew melon, slight berry acidity, and a long aftertaste.

Next, we added the blooming liquid (15ml) to this coffee and stirred thoroughly.

The re-measured concentration was 1.38%. In terms of flavor, the reintegrated Green Label Geisha displayed brighter citrus fruit acidity, overall higher sweetness, more prominent flavors, and a fuller mouthfeel.

Conclusion

In summary, we can conclude that the coffee liquid that permeates during blooming is also very important! The flavor compounds in coffee are limited and gradually decrease as extraction progresses. Although the extraction environment for hot water during blooming may not be as optimal as that for hot water poured during the formal extraction stage, the coffee grounds at this point contain the richest and most abundant flavor compounds. Therefore, even without ideal extraction conditions at the beginning, hot water can extract a large amount of flavor compounds, making this small amount of coffee liquid extremely concentrated (high content of flavor compounds per unit).

If we discard this highly concentrated coffee liquid, we not only lose rich flavor experiences but also reduce the fullness of the mouthfeel. Therefore, this counterproductive approach – losing both flavor and body – is not worth attempting~

Important Notice :

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