Basic knowledge of hand-brewed coffee purpose of brewing and steaming of coffee by hand-flushing three-stage water injection extraction

In front of the street, many novice hand brewers often ask a question: why is the hand brewing coffee steamed? One of the most indispensable steps in making coffee by hand is steaming. The purpose of steaming is to release gas and ensure uniform extraction of coffee, and to know clearly whether the beans brewed are fresh or not. Qianjie focuses on freshly roasted coffee beans, some people will mistakenly think that fresh coffee beans are freshly ground coffee, in fact, it has been secretly changed by the marketing means of some businesses. However, coffee beans are not as fresh as possible. if you get the coffee beans that have just been baked, you still need to keep them for four or five days, so that the coffee flavor can be completely extracted. The coffee beans served in Qianjie are usually served two or three days after the baking date, unless the guest asks for them to be baked on the same day.

Steaming purpose

Steaming, which is often expressed as Bloom in English, refers to the preparatory action of wetting a small amount of hot water evenly on the surface of coffee powder before formal water injection.

Qianjie through the experimental demonstration, there is no steaming, it is obvious that the extraction is easy to be insufficient. Because when extracting coffee, especially when some beans are quite fresh, there are more gases inside the beans, and the main purpose of steaming is to let these gases out. If there is no steaming, a large amount of gas inside the coffee powder will be released as soon as it comes into contact with water, and it will be boiled directly. Because the gas surrounds the coffee powder, it is difficult for the water to come into contact with the coffee powder, so it can only extract the coffee powder on the surface. Constantly scouring the extractable part, it is easy to produce uneven extraction.

Factors affecting steaming

The storage time of coffee beans, the baking degree of coffee beans, the level of water temperature, the amount of water, the length of steaming time and the degree of grinding. [storage time and roasting degree of coffee beans]

In two cases, the expansion rate is not obvious or even no reaction during steaming, which are freshness and baking degree.

First of all, there is a certain amount of gas in the fresh coffee powder, the gas in the coffee powder will be discharged slowly over time, and the coffee powder absorbs some moisture in the air, resulting in less gas, so stale ripe beans are less likely to expand or even unresponsive.

Second, the light roasted coffee beans are less likely to expand too violently, because the light roasted coffee beans are denser, so the overall gap is not as much as medium or deep roasting, so it contains less gas.

[the temperature of the steaming water]

The water temperature will affect the dissolution efficiency of the whole coffee. the higher the temperature is, the faster the dissolution rate is, and the more soluble substances are dissolved in the same extraction time, so generally speaking, the water temperature is too high to exceed 95 degrees Celsius. It is easy to make the bitter and astringent taste dissolve quickly. The lower the temperature, the slower the dissolution rate, and the less soluble substances are dissolved in the same extraction time, so generally speaking, the water temperature is too low, the coffee will be easy to thin, the good taste is not easy to extract, and steaming is not easy to complete.

[how much is the amount of water injected by hand]

A small amount of steaming water will lead to the situation that the coffee powder is not completely soaked, the coffee will have an obvious rough and astringent feeling at the entrance, and the afterrhyme of the latter section will be short; and if the steaming water is too much, the hot water in the steaming part of the front section will not extract enough coffee ingredients, the flavor of the extracted coffee will be relatively simple, and the acidity extracted in the front section will be obvious, thus masking other flavors.

[length of steaming time]

The length of steaming time depends on the freshness and baking degree of the beans. Generally speaking, the steaming time is about 30 to 60 seconds. When the expansion state of the coffee powder surface returns to calm, when the surface is about to shrink, it means that the steaming is complete. You can start the first water injection.

Qianjie coffee in the brewing beans for four or five days, the general steaming time is about 30 seconds.

[grindability of hand brewed coffee]

The thickness of coffee grinding will also affect the shape of the "hamburger" formed by steaming. When the grinding particles are thicker, the smaller the contact surface between powder and water, the less carbon dioxide the coffee releases.

When the grinding particles are too fine, although the contact surface with water is large, but because the powder is too fine, the water will stay on the surface, can not get under the water, and the condition of steaming will not be good.

Therefore, the hand punching needs to be suitable for the grind thickness and the steaming "hamburger" shape will be more obvious. Qianjie coffee uses a standard No. 20 sieve with a sieve powder pass rate of 80% (light baked beans) and 70-75% (medium and deep baked beans). To determine the grindness of each bean.

Steaming phenomenon of hand-brewed coffee: when hand-brewed coffee is injected into a hill, the gas in the coffee powder expands due to heat (when the coffee powder is enlarged, it will look like a honeycomb, with a lot of gaps). At this time, because the gas is constantly discharged, it will cause coffee powder and hot water to form an expanding hill on the outside. At the same time, in addition to the discharge of gas from the inside of the coffee powder, hot water also slowly seeps into the inside of the coffee powder, making the soluble substances of the coffee powder begin to dissolve and form a high concentration of coffee liquid. In the final stage of steaming, because the gas is almost discharged, the whole temperature decreases, and some undischarged air begins to retract, so from the outside, the hill will slowly dry or slightly crack and collapse, which also means that the steaming is complete, and you can start a second hand flush.

Steps for making coffee by hand

After talking about steaming, let's talk about the steps of hand-brewing coffee after steaming. The use of three-stage water injection in the front street will control the total extraction time at about 2 minutes, which can be divided into steaming, second water injection and third water injection. The segmented extraction method of three-stage water injection can clarify the flavor of the front, middle and back of the coffee and ensure the flavor of the coffee. [first water injection: stew (to help exhaust)]

Qianjie focuses on fresh baking. Freshly baked coffee beans accumulate a lot of gas (mostly carbon dioxide), which need to be kept for four or five days before cooking.

The steaming time of Qianjie coffee is set at 30 seconds. When the expansion of the coffee powder surface ends, you will see the coffee surface wrinkle, which means that the steaming is complete and water injection can be started. Basically raised beans, the shelf life of less than 1 month, Qianjie coffee for 30 seconds of stuffy steaming just can exhaust.

[second water injection]

The time of the second water injection, Qianjie coffee is filled with water for 30 seconds, when the timer shows 1 minute (including 30 seconds of steaming). From the middle, a small water column is injected into the bottom of the powder layer, so that the penetration force of the water column can be concentrated, the range of movement around the circle should be small, and then out. [third water injection]

Starting from the third water supply, Qianjie Coffee suggests observing the extent of the drop in the water level and starting the third stage of water injection before the powder bed is exposed. Also from the center to start the water supply circle, the amount of water should not exceed the height of the powder layer. Stop injecting water in 1 minute 50 seconds and finish filtering in 2 minutes.

Effect of step-by-step times of water injection on hand-brewed coffee

Qianjie also met some friends who asked why it is necessary to determine three-stage water injection. Will there be a difference between more or less coffee? Then Qianjie will come and do some experiments to see what the results are.

First of all, Qianjie takes the number of water injection sections as variables and carries out three groups of cooking respectively, in which the control group is the extraction mode of two-stage water injection after stuffy steaming, and group An is the extraction mode of only one stage of water injection after stuffy steaming. Group B is the extraction mode of three-stage water injection after steaming, and sips and evaluates it with a cup spoon after steaming.

The variable parameters are as follows:

Group

The first stage (steaming)

The second paragraph

The third paragraph

The fourth paragraph

Total water injection

Experimental group A

30ml

195ml

-

-

225ml

Control group

30ml

95ml

100ml

-

225ml

Experimental group B

30ml

65ml

65ml

65ml

225ml

This experiment uses the Yega Sheffield Conga Cooperative of Qianjie Coffee. The coffee bean information is as follows:

Name

Yega, Xuefei, Conga.

Altitude

1850 to 2050 meters

Variety

Primary species

Treatment mode

Sun treatment

[extraction parameters]

Powder quantity

15g

Powder-water ratio

1:15

Water temperature

91 ℃

Grinding degree

Medium and fine grinding (pass rate of No. 20 standard sieve 78%)

Filter cup

Hario V60 # 01

Water injection speed

4g/s

[experimental results]

Group

Total extraction time

Flavor description

Experimental group A

1 minute 43 seconds

The overall taste is light, the acidity of citrus is obvious, the fragrance of fresh flowers is high, and the finish is shorter.

Control group

2 minutes

Citrus, honey flavor, sweet and sour balanced, mild, juicy taste

Experimental group B

2 minutes 10 seconds

The sweetness is obviously improved, with citrus acid in the front, orange and yellow sugar in the middle, tea and astringency at the end, and the overall taste complexity is high.

[analysis results]

From the table, the most intuitive result is to prolong the extraction time and extract more substances. Increasing the number of water injection segments increases the interval time between segments, and during this increased interval time, coffee is still being extracted, so after increasing the number of stages, the total extraction time also increases, thus extracting more substances.

We know that time is an important factor affecting coffee extraction and coffee taste, too long extraction time can easily lead to excessive coffee extraction, coffee taste bitter hinder mouth; extraction time is too short, the extraction of coffee flavor substances are insufficient, coffee taste is easy to be dull and tasteless, can not show coffee flavor.

From the results of this experiment, it is believed that many friends will ask, "is the third paragraph the best water injection mode?" The answer is not necessarily, this experiment only obtains the result that the number of stages will affect the extraction time, rather than proving that three-stage extraction is the best water injection mode. One-stage water injection or multi-stage water injection can also adjust the extraction by adjusting other factors such as grinding or powder-water ratio. For example, Mr. Miyazhe's previous 46 brewing method used coarse ground coffee powder for five-stage water injection, and then introduced a fine grinding degree of one-stage water injection without steaming.

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