The effect of Grinding degree of Coffee Powder on Flavor how to determine the Grinding degree of hand pressing and Cold extraction

Why is my coffee so light? Why does my coffee have a bitter taste?! Is there something wrong with my way of cooking? No, there's something wrong with your grindness! The grinding degree of coffee beans determines the dissolution rate of soluble flavor substances in coffee. Of course, not all soluble substances in coffee are delicious, so it is very important to maximize the extraction of delicious flavor substances and avoid bad flavor substances precipitation, so it is very important to determine the size of coffee particles.

Different coffee utensils require different fineness of coffee grinding.

Different coffee utensils have different grinding degrees because of their different extraction methods. Take the hand-brewed coffee, French presser, Italian espresso machine and cold ice drops that we most often come into contact with as examples. The degree of grinding of the coffee from coarse to fine is listed as [French pressure pot > hand coffee > cold extraction ice drop]. Due to the different water temperature, method and time of extraction, in order to better extract coffee with the right concentration, it is necessary to find out the degree of grinding suitable for this extraction method.

However, because the grinder does not have a fixed scale value, the thickness of each grinder will be different, so we need to buy a cup calibration screen (that is, the aperture of No. 20 Chinese standard screen is 0.85mm).

How to use coffee grinding to calibrate the screen?

The aperture of No. 20 Chinese standard sieve is 0.85mm, which is used for particle size classification and particle size testing. As long as the standard sieve meets the factory standard, it is accurate. Coffee grinding calibration is also very simple, as long as the ground coffee powder is poured into the sieve, covered, shaken horizontally until no particles have fallen, and then weigh the particles passing through the sieve, so that you can know the thickness of the grinding, such as grinding 10g coffee powder, through 7.5g, then the grinding degree is 75% of the pass rate of sieve 20. The higher the passing rate, the finer the degree of grinding of the coffee.

How to determine whether the thickness of coffee powder is suitable for your own way of brewing?

Qianjie takes a cup test when it gets every new bean. The biggest purpose of cup testing is to determine the flavor and quality control of coffee beans without the interference of manipulation. Because the coffee is extracted by soaking at high temperature, the degree of grinding can not be too coarse and fine. The grindness used in the cup of coffee in the front street is 70-75% of the pass rate of the No. 20 sieve. Since the cup test can be calibrated by the standard screen to determine the grinding degree, we can also use the screen to determine the grinding degree in other cooking methods (except Italian concentrated extraction).

The grinding thickness of coffee powder suitable for autoclave extraction is: the pass rate of No. 20 screen is 68-75%.

The extraction method of the pressure kettle is very similar to that of the cup test, mainly by soaking, so the degree of grinding selected coincides with the height measured by the cup, and there is another reason for choosing the thicker grinding particles, that is, the metal filter is used in the pressure filtration. the gap is visible to the naked eye, and thicker is also chosen for better filtration. Coffee beans with different roasting degrees will have different degrees of grinding. it is recommended in front street that light roasted coffee beans (sour ones) can be moderately ground (pass rate 72-75%). Medium-deep roasted coffee beans (not very sour) can be ground with medium coarse grinding (pass rate 68-71%).

The grinding thickness of coffee powder suitable for hand extraction is: the pass rate of No. 20 sieve is 70-80%.

Hand brewing coffee is mainly drip filter, which is different from soaking for a long time and is easy to brew bad flavor. the brewing time of hand brewing coffee is short, about 1 minute 30 seconds to 2 minutes 30 seconds. Therefore, it needs to be finer than the grinding degree measured by the cup in order to fully express the flavor of coffee. It is recommended in Qianjie that light roasted coffee beans (with sour taste) can be ground by medium and fine grinding (pass rate 75-80%), and medium-deep roasted coffee beans (with no sour taste) can be moderately ground (pass rate 70-75%).

The grindability of coffee powder suitable for cold extraction / ice drop is: the pass rate of No. 20 screen is 75-80%.

Different from hand punching / pressure, cold extraction / ice droplets are extracted by low temperature immersion. The bitter substances extracted at low temperature are much less. By prolonging the extraction time and fully infiltrating the coffee powder, it is easier to extract small molecular flavor substances, such as flower aroma, fruit aroma and so on. However, because the two coffees need to be extracted for a long time, if too fine will make the cold-extracted coffee cloudy and prone to woody taste, the ice droplets will also have powder stratification / blockage. Qianjie suggested that light roasting coffee beans with medium and deep roasting can be ground by medium and fine grinding (pass rate 80-85%).

The grindability of coffee powder suitable for espresso machine (this can be corrected by sieve because it is too fine)

Qianjie stores debug espresso every day before opening, a large part of which is the need to adjust the degree of grinding. As the espresso machine is very sensitive to the fineness of coffee powder, the grinding scale of 0.1 grid may be different, and the extraction time and flavor will be different. In Qianjie, for example, the Italian extraction scheme in Qianjie is that 20g coffee powder extracts 40g coffee liquid in 28 seconds (error is ±1). First, the extraction scheme is fixed, and the extraction scheme is achieved by adjusting the grinding degree. Then determine whether the parameters need to be fine-tuned by tasting the flavor.

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