Coffee Xiaobai must learn the basic operation flow of hand-brewed coffee: three-stage water injection coffee extraction method

With regard to the question of "how to make good coffee", many friends know that as long as there is the right grinding degree to brew coffee with the right water temperature, the right proportion and a steady flow of water, the coffee is basically not bad. But few people notice that the number of stages of water injection can change the taste of coffee.

What is three-stage extraction?

What are the changes in coffee when water is injected in stages?

Three-stage extraction means that the amount of water needed is injected in three stages throughout the coffee extraction process. During the whole process of water injection, waiting, reinjection, waiting and reinjection, although the temperature of the injected water will continue to drop, the temperature of the water injected into the filter cup is constantly fluctuating.

Because of the large difference between the thermal insulation performance of the hand-flushing pot and the water in the water injection filter cup, the water temperature in the filter cup-the temperature of the powder layer will decrease obviously in the same waiting time, while the water temperature of the hand-flushing pot is only about 1 ℃. Therefore, the coffee powder layer will be in the process of heating up, cooling down, heating up again, and then heating up again, thus releasing flavor substances with different tastes.

What is the effect of wavy changes in water temperature

Which coffee flavors are extracted at different temperatures?

First of all, when the first section of water is injected, both the water temperature and the powder layer temperature must be the highest in the whole extraction stage. under the action of sudden thermal molecular movement, carbon dioxide in coffee particles will quickly become active and form a large number of bubbles between the particles. these bubbles seal the surface of the particles, so that the flavor substances inside can not be effectively released.

As the old saying goes, the freshness of coffee beans is very important, and the fresher the beans, the more carbon dioxide there will be. Therefore, it is necessary to have a long stay after this period of water injection (the longer the bubbling time on the surface of the powder layer, the more carbon dioxide).

According to the exhaust degree of coffee beans, hand steaming time is recommended between 20-40 seconds, let carbon dioxide return to the air, reduce the formation of bubbles in the powder layer, contribute to the stability and uniformity of coffee extraction (flavor substance release). During the steaming process, the temperature of the powder layer will continue to drop, and the coffee particles will release carbon dioxide in the first 2 of the time, and the rest of the time will begin to release sour substances, such as citrus fruits, berries and other sour substances will be released in the first stage.

After the second stage of water injection, the temperature of the powder layer will rise again, which is the best time to extract sour and sweet flavor / aroma substances. So if you are medium-roasted coffee beans / aroma-rich coffee beans, you can choose to reduce the water injection rate (3-4G per second) in this extraction stage, so that the extraction time of the second stage can be slightly extended, so that the pleasant flavor substances can be extracted more fully.

Due to the water injection in the first two stages, the heat of the powder layer will be relatively balanced at this time, so the temperature of the powder layer will not be very different from that of the second section after water injection in the third stage, about 2 ℃. At this stage, the substances that form the main flavor of coffee have been basically extracted, and the rest is the release of macromolecules (bitter substances), shaping the thickness of alcohol for coffee & increasing the overall sense of hierarchy. So at this stage, you can re-adjust the water injection rate (4-5g per second) for extraction to avoid excessive extraction in the later stage leading to the smell of wood.

The biggest advantage of three-stage extraction is that the release degree of a certain type of substance can be controlled by the size of each stage / the amount of water injected, so that the coffee flavor can be presented differently.

If there is no sectional water injection

What will the coffee taste like?

First of all, the main purpose of segmenting is to let the coffee particles release carbon dioxide in a certain period of time, so that the later extraction is more stable. If you directly inject water at one time (without steaming), carbon dioxide will constantly form bubbles between the coffee particles and rise, making the flow through the particles uncontrollable, resulting in uneven coffee extraction.

Even if the beans themselves do not have much carbon dioxide, segmented extraction is still necessary. In the case of shallow roasted coffee, the lighter the roasting, the higher the density of the beans themselves, and the more difficult it is to release flavor substances. This will lead to such a situation: water constantly washes away the substances on the surface of coffee particles, while the internal substances are not released in time. The final coffee will also be due to excessive extraction of surface substances, resulting in coffee insipid and unpleasant astringency. This also explains why underextracted coffee also has an astringent taste.

Of course, it's not that you can't make good coffee without injecting water in stages, but only if you have a good understanding of coffee beans and opinions on brewing, and then adjust the brewing parameters and methods. So if you want to have more layers of coffee, three-stage extraction is the best choice. It is important to note that the more levels you get, the better. Too many segments are easy to backfire.

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