[Experiment] When pouring water into a brewed coffee, is it true that the coffee powder on the outer circle cannot be brewed?

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After watching many videos and brewing many cups of coffee, I believe everyone is familiar with hand brewing coffee. But do you have this question: Should I brew the coffee powder on the periphery? Should I brew the water on the periphery? Regarding this question, today I plan to talk about it in two parts.

§1|Steaming

The general method of steaming and pouring water in hand-brewed coffee is to pour water from the center to the outside in a circle. So should we pour water directly to the outside to soak the coffee powder? Or should we pour water in a small area in the center and use the water to diffuse to the outside to soak the coffee powder? What effect do the two have on the flavor of the coffee? Let's actually do it with this question~

We used coffee beans of three roasting degrees, light, medium and dark, to do this brewing experiment to explore the flavor difference of whether the steaming water injection wets the outer coffee powder. The reason for choosing three roasting degrees is that for coffee beans of different roasting degrees, the exhaust and water absorption rates are different, and the difference in steaming state can be observed.

The brewing method after steaming is uniformly divided into two stages of extraction, keeping the water injection method consistent.

Test 1: Sidamo Oiran lightly roasted

Test 2: Yemeni Mocha Matali Medium Bake

Test 3: Sumatra Gold Mandheling Dark Roast

Skipping the experimental records, let's share the test results directly:

The first two groups of coffees tested without steaming around the outside will have grassy taste and under-extraction greenness and sourness, but the impact on the third group is not obvious (dark roasted coffee exhausts quickly, and water passes through the powder particles quickly). Through tasting, it was found that the impact of whether the outer powder layer is wetted during steaming on the flavor is mainly reflected in the uneven extraction caused by the difference in water absorption time of the coffee powder during the extraction preparation stage. The purpose of steaming is to quickly soak all the coffee powder so that the coffee powder can be evenly hydrated and exhausted in the closest time.

In the group without an outer ring, since water penetrates from the inside to the outside, when the coffee powder in the center reaches the soaking state, the coffee powder on the periphery has just begun to soak in water, which causes inconsistent extraction rate, especially light roasted and medium roasted coffee will have a green and under-extracted taste.

When pouring water around the outer circle for steaming, a phenomenon will occur. The water will penetrate from the outside to the inside, and the coffee powder in the center will be blocked from venting outwards. It will vent upwards and bubble continuously, making it look like the steaming has failed.

The key to using central water injection is to allow the water to wet all the coffee powder as quickly as possible, so as to achieve the goal of "fast". When steaming, there is not much difference between injecting water in a small area to penetrate the periphery and directly injecting water to the periphery. In addition, the problem of insufficient steaming can be compensated by slightly extending the steaming time.

It should be noted that if small bubbles continuously appear in the same place when steaming the middle part, it means that the steaming of this part is insufficient, the force of the water cannot reach the coffee powder at the bottom, and the exhaust of the coffee powder is blocked during the water penetration process. You can then improve the extraction rate by quickly and forcefully rotating the water and "stirring" the coffee powder at the bottom to make it roll.

§2|Handling the outer coffee powder during extraction

We have emphasized in past articles that brewing should not go around the outer circle to avoid "washing the filter paper", that is, the water flow penetrates the coffee powder layer and washes the filter paper, causing the water to slip away from the edge of the filter paper. Such coffee will be bland.

Water is poured around the central "one yuan coin"↓

Water injection around the periphery ↓

Moreover, when the water flows to the outer layer, it will concentrate the coffee powder in the middle of the filter cup, increasing the thickness of the powder layer. This will cause the coffee to be in a brewing state without proper tumbling extraction, which can easily make the coffee taste watery and astringent.

If you are worried that the coffee will not taste good because the coffee powder in the outer circle is not extracted, you might as well think about it from another angle - why bother with that small circle of coffee powder? It is a risky method to directly pour water to the outer part, and the editor does not recommend it. You can stir the outer coffee powder into the center by quickly circling and pulling the water flow up and down, but be careful not to over-extract!

Finally, there are some tips to deal with the outer coffee powder, that is, shaking the cup and stirring. The two methods are mainly used to deal with lightly roasted or finely ground coffee. These two methods can effectively make all the coffee be extracted. Shaking and stirring the cup during steaming can accelerate the exhaust and infiltration of the coffee, avoiding uneven/insufficient steaming due to slow water penetration. Stirring during extraction and shaking the cup at the end of extraction can increase the extraction rate (also be careful not to over-extract), speed up the water entry speed, and avoid soaking for too long.

The above are some explorations and suggestions on the processing of peripheral coffee powder. I hope it will be useful to everyone~

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