Frequently asked questions for newbies in making coffee! What is the reason for the bitter taste of hand-brewed coffee? What is excess?

Many friends always face excessive troubles when they first start! The so-called "over-extraction" refers to excessive extraction. The substances that can be dissolved by water in a coffee bean account for about 30% of the total. Although there is only so much, we cannot dissolve everything. Because in addition to those pleasant substances that make us feel happy, there are also some unpleasant substances that can cause negative manifestations such as bitterness, astringency, and miscellaneous coffee. When these substances are dissolved in large quantities, the entire cup of coffee will become unacceptable. So when this occurs, we call it excessive.

If we don't want to drink a miserable, over-extracted coffee, then it's best to find the right extraction parameters and control the extraction rate of the coffee. (Insufficient extraction will also make the coffee taste astringent, bitter and miscellaneous, but it will not be so prominent.) Among the many parameters, grinding, water temperature, and time are the three key factors affecting extraction. So today, Qianjie came to share how to adjust and correct these parameters when the coffee we brewed appears to be too strong ~

The first thing we need to question about the grinding of coffee powder is the grinding of coffee powder, because many novice friends often have problems with grinding and cause the coffee to be over-extracted. After all, grinding does not have a very intuitive value like other parameters, so this leads to most of the time, we can only judge a rough idea through the naked eye, and then it is easy to make the coffee over-extracted due to misjudgment. (Guess which of the two coffee powders in the picture below is ground coarsely)

(The answer is revealed, the one on the right is thicker! The left is 85% sieving rate of the No. 20 sieve, and the right is 75%) The above figure is an example. When grinding a lightly roasted coffee bean, the thickness we need is fine sugar particles, and the sieving rate is 75% of the No. 20 sieve. However, what is currently used is a coffee powder with a sieve rate of 85% on the No. 20 sieve. Judging by the naked eye alone, it is difficult for us to tell that the coffee powder is thinner than the set value, but we just think it is about the same, and then we start to brew it. Because the coffee particles are thinner and have a wider water-contacting surface area, the dissolution rate of the substance is improved. With other parameters unchanged, this will cause the coffee to dissolve more mass than we thought, and then there is a probability of overextraction.

So if we are brewing according to a certain formula, but find that the final brewed coffee is bitter and full of miscellaneous flavors, we can first roughen the ground. By thickening the particle value of coffee powder to reduce extraction efficiency and prevent over-extraction. After all, other parameters are visible. When the values of other parameters differ from the values in the formula, we can directly capture and correct them. So if you want to know an approximate value of the coffee powder ground at the current grinding degree, Qianjie recommends that you can purchase a No. 20 sieve online, which will allow us to get an approximate range. For example, Qianjie often mentions that the sieving rate of No. 20 sieve is 75%, which means that the amount of ground coffee powder that can pass through the sieve accounts for 75% of the total.

But what we need to know is that the screening rate can only provide you with a rough reference. For example, 75% of the amount sieved is, but how fine and uniform the 75% of the coffee is, and how much is extremely fine powder is not something that it can judge. (Related article → How to use the No. 20 sieve) In addition to the coffee powder being ground, there is another grinding problem that can cause the coffee to be easily overextracted. That is, the grinding quality is not high enough and too much extremely fine powder is ground.

When the quality of the bean grinder is not high enough, not only will the ground coffee powder be very uneven in thickness, but there will also be a lot of fine powder. Qianjie often mentions that the presence of a suitable amount of fine powder can help improve the level, but once excessive, the coffee can easily become over-extracted! Because the substances in the fine powder will be dissolved more easily, including bitter substances. Not only that, because the fine powder is extremely small, it will easily block the filter paper during brewing, prolonging the extraction time, and allowing other normal-sized particles to be excessively extracted.

In this case, Qianjie would suggest using a powder sifter to remove part of the fine powder before starting formal brewing. For specific matters, please refer to Qianjie's previous articles, but I will just repeat them here ~

Excessive extraction time is followed by extraction time, which refers to the time it takes for water to come into contact with coffee powder to dissolve the substance. The longer the extraction time we use when brewing, the more substances will dissolve out. In other words, the longer the time it takes to extract, the more likely the coffee is to be overextracted. But there is no standard for how long the time should be, because no matter how long the extraction time is 2 minutes, 3 minutes, or 4 minutes, we can still make a delicious pot of coffee. The specific situation depends on the matching between time and other parameters. Whether it is suitable, just like "What degree of water is best to make coffee?" shared by Qianjie some time ago? Same.

Again in that example, when Qianjie brewed a pot of 15g lightly roasted coffee, the parameters used are: "Water temperature is 92°C, powder-to-water ratio is 1:15, and grinding degree is 75% of the sieve of No. 20 sieve. Rate, combined with three-stage brewing." Under this parameter, 2 minutes to 2 and a half minutes is the optimal extraction time for this parameter. If the time goes to 3 or 4 minutes, then the extraction time will be too long for this parameter, and there is a high probability that the negative manifestations of coffee such as bitterness, impurity, and astringency will be washed out. If the time really goes to 3 or 4 minutes, then at times like this, we need to appropriately reduce the extraction time and reduce the negative substances that are dissolved. There are many factors that affect time, such as the fine powder blockage mentioned in Qianjie earlier is one of them. There is also the use of filter cups! The size of the drainage hole of the filter cup, the number of diversion ribs, and the degree of protrusion will have a direct impact on the drainage speed. If we want to shorten the extraction time and increase the drainage speed, we might as well use a fast-flow filter bowl like the V60 with prominent ribs and a large drainage hole.

In addition, time will also be controlled by our water injection rate. Without forming a plug, the higher our water injection rate, the faster the water injection rate will be and the shorter the extraction time will be, and vice versa. So if we want to shorten the extraction time, it is also a good way to increase the water injection rate appropriately. (Simply put, it means increasing the water flow and injecting more hot water at the same time)

The water temperature is ultimately the water temperature. The water temperature determines the rate of dissolving substances. However, because of the previous article "What degree of water should I use to make coffee?" Share it in detail, so I won't go into it too much here. But in fact, the water temperature is the best to judge. Generally, if other parameters are not too extreme, the water temperature will be in the range of 86 to 93°C. Again with the above parameter, if other parameters remain unchanged, the water temperature of Qianjie will be controlled within the range of 86 to 88°C when brewing deep-roasted coffee; while when brewing medium-light to light-roasted coffee, it will be controlled within the range of 90 to 93°C. When we feel that the brewed coffee is too bitter, we can reduce the extraction efficiency by appropriately lowering the water temperature.

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