Characteristics of advantages and disadvantages of hand-brewed coffee by central water injection Analysis of segmented Circle injection of hand-made Coffee

Qianjie mentioned in the article "the Science of Water injection" that circular water injection has obvious advantages over central water injection, and the central water injection method is not as powerful as stability and uniform extraction alone.

This time we will switch to the perspective of central water injection. If there is really no merit in this method, then it should only be found in historical records now. In fact, there are quite a few people who use this method to make coffee! We might as well do a comparative experiment, which also uses central water injection and circular water injection to compare, in view of the fact that the flow of central water injection is slightly angled in the last comparison, it will produce turbulence. Therefore, a small flow is used this time, so that the flow is not easy to appear at an angle.

This time, the method of water injection is one-size-fits-all, and the stifling stage is still water injection around the circle. After confirming that there is nothing wrong with the powder pit, test the concentration of the two cups of coffee. The results show that the concentration of central water injection is 1.23% and that of circular water injection is 1.10%.

In other words, in the case of small flow, the extraction rate of central water injection is higher than that of circular water injection. Qianjie found two possible reasons for this result. The first reason is the temperature, although everyone's pot temperature is the same, but in the powder layer to participate in the extraction of water temperature is not necessarily the same. If you pay attention to the article "what's the difference between a high water column and a low water column to make coffee" in front of the street, you will know that the high water column has more contact with air and loses more temperature, resulting in a lower extraction rate of high water column than that of low water column. Similar to this situation, static water injection comes into contact with less cold air than circular water injection, so it is more warm. The second reason is that the central water injection comes into contact with more coffee powder. Most of us still use tapered filter cups to make coffee. This filter cup has a feature: the top is wide and the bottom is narrow, the middle layer of powder is thick, and the surrounding layer of powder is thin. From the perspective of overlooking, circular water injection does achieve "uniform water injection", but it may not be seen from the side.

While the central water injection, the thickest powder layer in the middle can be fully extracted, and the water also has the effect of diffusion, which will spread around and supply to the thinner powder layer around. In this way, there is less water to sneak away and more substances to extract coffee.

In the same experiment, Qianjie tasted the coffee after testing the data. Qianjie found that the coffee flavor of the central water injection is more concentrated, and there will be a bitter taste. However, the water injection around the circle is quite soft and comfortable. It seems that the extraction rate calculated from the test concentration only represents the overall extraction. In fact, the central water injection leads to the unbalanced extraction with high central extraction rate and low surrounding extraction rate, which averages the overall extraction rate measured in Qianjie. Next, let's take a look at the difference between three-stage central water injection and circular water injection. The parameters are basically the same as above, so they are replaced by three segments. The measured concentration of central water injection is 1.32%, and the concentration of circular water injection is 1.45%.

In this round of comparative experiments, on the contrary, the extraction rate of water injection with small flow is higher. This is because the height of the powder layer is lower than that of a knife flow, and the water injection time is prolonged, that is to say, the scouring effect of the water column is more significant in the second half. Also thanks to the fact that the water level is not raised, there is less water slipping away from the edge. Therefore, from these experiments, it is easy to explore the combination of coil and central water injection. The more mainstream brewing and cooking logic is to use three-knife flow extraction, first to inject water as usual in the steaming stage; the first knife to inject water around a circle to achieve uniform penetration; the second knife to inject water around a small circle to ensure extraction and reduce disturbance; and the third knife to use central water injection to restrain extraction and avoid smells.