What is the difference between one-step flow and three-step flow? Why do I need water to make coffee by hand? What are the advantages of three-stage water injection for hand-brewed coffee?

Hand coffee has a lot of ways to inject water, just familiar with there are three-stage, one-knife flow, four or six, or drip method, and so on!

But even if there are so many ways of cooking, people are always more inclined to use multi-stage cooking. Whether it's on the field, in a coffee shop, or an individual. As a result, many beginners are curious and ask Qianjie, "Why does the water injection of hand-brewed coffee always like to be divided into multiple stages?"

What is "segmented water injection"? The so-called segmented water injection is to divide the total amount of water we need to inject into multiple times. Because the existence of the preliminary action of steaming has become a consensus, so with regard to sectioning, our main understanding is that after steaming and water injection, the remaining water is injected into one stage or more than two stages.

After steaming, the total water is boiled in one breath, while it is divided into more than two stages and injected several times in three-stage, four-or six-stage, or other cooking methods. It is not difficult to find that the main question at the beginning is: why people prefer to use more than two injections of coffee rather than one-size-fits-all injection of coffee. In fact, the answer is very simple, and there are two reasons why people are more inclined to use multi-stage water injection: one is that multi-stage water injection can improve the extraction efficiency, and the other is that multi-stage water injection is more controllable for cooking.

The first advantage of multi-stage water injection: to improve the extraction rate compared with one-time water injection, the advantage of multi-stage water injection is to improve the extraction rate, and here is divided into two factors: the first is the extraction time! The most obvious difference between multi-stage water injection and one-stage water injection is that the extraction time will be longer, because the segmented water injection has several more waiting time, and the next section can be injected only after the previous injection of hot water has flowed down. So the more paragraphs we divide, the longer the total extraction time will be because of the increase in waiting time.

The extraction time is the contact time between water and coffee powder, so the longer the extraction time is, the higher the extraction rate of coffee is. Under the same parameters, the extraction rate of multi-stage water injection is higher than that of one-stage water injection. Another reason is the poor concentration! As we all know, we extract coffee mainly by using water as a solvent to extract the substances from the coffee powder, and here it is mainly carried out through the concentration difference. Under the same parameters, the lower the coffee concentration in the water, the faster the dissolution rate, while the higher the coffee concentration in the water, the lower the dissolution rate. At this point, Qianjie would like to issue a question that you can think about: why is it that immersion extraction such as French kettle and smart cup may not be too extractive for ten minutes, but trickle-filter hand-brewed coffee will pour out a cup of over-extracted coffee in just 2-3 minutes?

Did you come up with the answer? One of the main reasons is the concentration difference. The reason why the immersion type can be soaked for a long time is that the concentration of the liquid around the coffee powder is increasing, and the extraction efficiency is getting lower and lower. Assuming that the initial concentration of coffee in the water is 0, it must have dissolved very quickly at that time. However, when more and more coffee substances are dissolved and the concentration of coffee in the water is getting higher and higher, the extraction efficiency becomes lower and lower, because the concentration of coffee powder tends to be consistent inside and outside, so it is naturally difficult to extract substances from it.

Hand-brewed coffee because of the continuous injection of "fresh" hot water, so the liquid concentration is constantly "refreshed". Therefore, this is why it is often said that immersion extraction is more fault-tolerant than trickling extraction and is not easy to extract. It's a little far around, but it's the same when we apply the principle to the injection of hand-brewed coffee. If we inject hot water in one breath while making coffee by hand, the hot water in the filter cup will make the extraction rate lower and lower because the coffee concentration is getting higher and higher, after all, it will not run out quickly; if it is divided into multiple stages, the concentration of the water can be constantly refreshed so that the extraction efficiency can be maintained. Therefore, under the same parameters, multi-stage water injection will have a higher extraction rate than one-time water injection. In addition, there are relatively small effects such as scouring efficiency, and Qianjie is no longer introduced too much here.

The second advantage of multi-stage water injection: it is more controllable and can better control the extraction time! When we divide the water injection into more than 2 stages, we can better control the extraction time within our own ideal range.

For example, under the same grinding scale, the thickness of coffee powder will vary according to the degree of baking and treatment, and these differences will directly affect the penetration rate of coffee liquid. The extraction time set in Qianjie is 2 minutes. If we want to control the extraction time of all coffee beans at two minutes, then, in addition to adjusting the grinding, there is also the control of the injected water flow. Qianjie uses three-stage cooking, which can be measured by observing the launching time of the second stage of hot water to measure how the third stage of hot water is injected, and then control the extraction time. When the second stage of hot water permeates faster, the extraction time will be prolonged by reducing the flow of the third stage, while if the second stage of hot water permeates more slowly, the extraction time will be reduced by increasing the flow of water in the third stage (for example).

But if you use one-size-fits-all injection, you can only watch the hot water clog or run out directly, and there is no adjustment. Therefore, the combination of the above two points, we can know why hand-brewed coffee is best divided into multi-stage injection. Of course, it is not that one-knife flow is not easy to use, but one-off injection such as one-off flow has higher requirements for the adaptation of parameters.

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