How to control the water temperature in hand-brewed coffee? Is the effect of 1 ℃ difference in water temperature really great?

Guide reading

Water temperature is one of the four elements of brewing, which can be said to have an important effect on the flavor of a cup of coffee. So how do we determine the temperature of the water we usually cook?

The temperature of water

Generally speaking, we recommend that the water temperature of brewing hand coffee is between 86 and 93 ℃, in which 90-93 ℃ is recommended for light roasted coffee, and 86-89 ℃ is recommended for medium and deep roasted coffee. So how did you get this range?

First of all, we have to start with the extraction efficiency of water, when the higher the water temperature, the higher the extraction efficiency of coffee, the easier it is to extract the substances from coffee beans, and the higher the concentration of coffee, of course, the easier it is to extract bad flavor substances, that is, excessive extraction; the lower the water temperature, the lower the coffee extraction efficiency, the more difficult it is to extract coffee beans, and the lower the concentration of coffee, but it may lead to insufficient extraction. So we know that normal temperature water and boiling water are not suitable for brewing coffee.

Second, coffee associations such as SCAA and SCAE, which are based on data science, and advances in technology, it is easy for us to look at things on the shoulders of these giants. The extraction efficiency of water temperature between 86-93 ℃ is very easy to reach the extraction rate of 18-22%. After many tests in Qianjie, it is found that the flavor of most medium-and light-roasted coffee can be stably brewed when the water temperature is controlled at 90-91 ℃.

Is the effect of 1 ℃ difference in water temperature great?

The difference of water temperature by 1 ℃ will definitely have an impact, but is it really significant? Therefore, a comparative experiment was carried out in Qianjie, using 89 ℃, 90 ℃ and 91 ℃ respectively to brew Yega Xuefei coffee (recommended water temperature 90 ℃). Except for the water temperature, the other parameters were as consistent as possible. The results are different, but not very obvious, without horizontal comparison, it is difficult to distinguish, and the measured coffee concentration is 1.26%, 1.27%, 1.30% respectively.

Of course, the difference in water temperature in the kettle by 1 ℃ does not have much effect on the opponent's coffee making, but this is not the triumph of "almost" doctrine (as the so-called "butterfly effect", a slight difference may lead to a different outcome). Because there are many factors that affect the water temperature, the water temperature that effectively participates in the extraction of coffee powder is the water temperature in the filter cup, not the water temperature in the pot, and this gives rise to a problem: if the water temperature is to be determined, it should be the water temperature when it comes into contact with coffee powder in the filter cup, but it is difficult to determine the water temperature in the filter cup, so we can only take the water temperature in the source pot as a reference.

What else affects the water temperature?

If you only take the kettle temperature as the basis for the water temperature, there are indeed too many uncertainties.

1. The heat preservation of the pot. You know, brewing coffee is an extraction process, and pots of different materials have different heat preservation properties. For example, copper pots are warmer than stainless steel pots. When the equivalent is 90 ℃, the water temperature is 86.4 ℃ after 1 minute and 30 seconds. The water temperature of stainless steel is 83.6 ℃ after 1 minute and 30 seconds. The amount of water in the kettle will also affect the rate of cooling.

2. The height of the current. An experiment has been done in Qianjie to find out why the concentration of water injection in high water column is lower than that in low water column. The main reason is that the larger the surface area of water column exposed to air in the filter cup, the faster its cooling rate.

3. The heat preservation of the filter cup. The actual coffee extraction temperature must be lower than the pot temperature, for example, the ceramic filter cup has a maximum extraction temperature of 87.7 ℃ (pot initial temperature 91 ℃). If the ceramic is not pre-heated, the extraction temperature will be even lower (the highest temperature is 86.9 ℃).

Water temperature is a very important parameter, but the water temperature we are talking about not only refers to the initial temperature of the kettle, but also the temperature change after coming out of the spout is also worthy of our deep study, and the real water temperature is actually the temperature in the extracted coffee.