How to cook a "good" Espresso

To brew a cup of "good" Espresso coffee, there are a variety of factors that need to be discussed:

Composition, roasting and preservation of coffee beans

Grinding, weight and filling of coffee beans

Initial temperature and temperature retention of cooking

The pressure of cooking

The amount of extraction

Other additives

If you can control all the above factors from beginning to end, "good" Espresso coffee should be easy to get. However, how to control the above factors one by one and make cups of "good" Espresso coffee handily, we will wait for the next issue!

Grinding, weight and filling of coffee beans

This is the first priority that we intend to embark on. It is "easy to control" and "influential".

Since Espresso coffee refers to coffee brewed under pressure, the "coffee cake" will face "pressurized hot water" rather than ordinary hot water. In other words, the "coffee cake" should be able to be closely combined to a certain extent, so that the pressurized hot water can slowly pass through the "coffee cake", otherwise the pressurized hot water will leak, how can we bring out the essence of the coffee powder in time. But the "coffee cake" should not be too tight, otherwise if there is no way to "break through" the "coffee cake" in pressurized hot water, there will be no coffee to drink.

How should "coffee cakes" properly face "pressurized hot water"? There are three factors that can be discussed together: "grinding", "weight" and "packing". We have reason to prove (as can be seen from a simple experiment) that these three variables should be considered comprehensively, because they are interrelated and directly affect the "intensity" of "coffee cakes". Referring to other data, we can have a "quantitative" basis for judgment. For example, the extraction time should be between a few seconds and several seconds, and the color should be so-and-so or so-and-so.

I must emphasize that all of the above can help us judge whether to make a good cup of coffee, but I must also emphasize one point: "you have to drink it!", "drink it and see what it tastes like!" and "drink it and see if it's the taste you like!" If it's not what you like, it's not good coffee, even if it meets all the criteria, the time is right, the weight is right, the color is right. Oh, but that doesn't work. It doesn't count until you feel good. I even suspect that many "very good brewers" use a meter to make coffee, use a barrel to make coffee, and then "admire" Klima with their eyes, and then pour it out. I think this is not the purpose of "brewing coffee"? "brewing coffee" is to "drink coffee", not to "watch coffee"!

Assuming that everyone has accumulated the tongue training of dozens of gallons of Espresso coffee, that is, the basic ability to recognize "which is good" and "which is bad", we can do the following little experiment:

Experiment 1: measurement of cooking time

Objective: to understand the significance of "grinding thickness", "weight" and "packing" of coffee powder.

Step 1: get your Espresso machine ready, follow the handle on the shelf with "single coffee dish (single filter)", the coffee dish does not need to be filled with coffee powder; write down the 30-inch mark on the cup, if it cannot be accurately measured, draw a scale directly on the commonly used liquid surface according to the brewing habit, from 25 to 40 grams, it doesn't matter, beyond this range is usually not very meaningful. Press the brewing button to hold 30 kilos of hot water in a cup. Please repeat this action many times (8 to 10 times), and write down the time each time. It is important to note that the calculation time starts from the first drop of water (not by pressing the cooking key) and ends with the scale mark drawn on the cup. If you average multiple times, the range of error should be very small, unless the machine is quite unstable. This average is called "T0". It is also important to wait for the machine to say it is ready to cook (household machines usually have "cooking lights") in order to really get rid of other factors. The time from "pressing the boiling button" to "dripping the first drop of water" is defined as "Tl", which means "outlet delay time". Generally speaking, "Tl" is usually within a very short period of seconds.

Note 1: 30 "means that under all the conditions I am used to, I think that a cup of Espresso should be 30", and everyone has a different combination of conditions (coffee beans, machine, personal taste …...) So it doesn't have to be 30 years old.

Step 2: repeat step 1, but the coffee dish should be filled with coffee powder as usual, that is, the coffee is actually brewed. The so-called habitual practice refers to the "grinding thickness", "weight" and "packing" that you are used to. It also records the time it takes for coffee to reach the scale, and it also averages it. But this time, please start with "pressing the brewing button", calculate the time until "the cup receives 30 kilos of coffee", and then subtract the "effluent delay time" or "Tl" one by one. If the error range is too large, please do it a few more times, and remove the excessive error (OUTLYING) to keep the same number of observations. This average is called "Tf".

After "step 1" and "step 2", you will get a "damping factor" value, or "porosity" (Note 2, Note 3). The term "porosity" is generally used in the "fast filtration" of "environmental engineering". It uses some "filter materials" and lays them layer by layer according to different thickness. When water flows through these "filter materials", the flow rate will slow down (because of hindrance), thus achieving the effect of filtration. When you see this, you must all understand that "coffee cakes" are "filter materials" to "block" the passage of pressurized hot water. If the "Tf" is generally less than 20 seconds, it means that the "hindrance" is not big enough, and the "pressurized hot water" does not have time to bring out the essence of the coffee powder; on the contrary, if the "Tf" is generally higher than 30 seconds, it means that the "hindrance" is too big, and the "pressurized hot water" cannot successfully "break through" the "coffee cake".

Therefore, if the recording time of step 2 is too different from each other, it means that the "hindrance" is different each time, which is very serious! This means that you can only try your luck and don't know how to make "good" coffee.

In the experiments done on my machine, "Tl" is about 1.5 seconds, "T0" is about 3.5 seconds, and "Tf" is about 22 seconds. "Tf" is about 6 times that of "T0", that is, the "damping factor" is 6 (after filling coffee powder, the resistance is increased by 6 times), and the "porosity" is 1/6 (after filling coffee powder, the pores available for hot water flow are reduced to 1/6).

Note 2: both "damping factor" and "porosity" have their real academic definitions. Here, it is merely to borrow the imagination provided by this term to imagine that "resistance" becomes larger and "porosity" becomes less. Therefore, it is not necessary to adhere to the original academic definition, just for imagination.

Note 3: the meaning of "Tf" is based on: in all the conditions I am used to (coffee beans, machines, personal taste …) In this case, if you happen to get a 30-year-old Espresso in the time of "Tf", then this cup of Espresso makes me feel good the most times. Other conditions (such as 35 seconds, 28 seconds; 20 seconds, 25 seconds) are not necessarily wrong! But: the number of times it makes me feel good is less. So I use quantifiable results: "30" and "Tf" to improve the feasibility of "I think it tastes good", instead of saying "30" + "Tf" = "must be delicious".

The damping factor is 6 and the porosity is 1/6. The simple meaning of this set of figures is: when other factors do not change (fixed pressure, the same brand of coffee powder …) As long as you add a "damping factor" of 6 to make the "porosity" 1/6, no matter how much you "grind", how much "weight", how hard you "fill". In theory, the result should be the same. The results include that the coffee is 30 grams and the extraction time is "Tf". However, there is no guarantee that "you will also feel good". In other words: you can grind it thicker, but press it tighter: or have more portions, but loosen it a little bit. You will get 30 packs of coffee in "Tf" time. However, there is no guarantee that "you will also feel good".

Generally speaking, the grinding should not be too thick and the weight should not be too small, because you are not a machine and you cannot press too hard, nor too much, because the machine manufacturer has designed the size of the "coffee dish", no matter how much it cannot be filled. At the same time, it's just a waste of coffee powder.

Therefore, all you can do is to fix the "filling method" and slightly adjust the "coffee powder content", focusing on adjusting the "grinding thickness". Then find a way to get a set of quantifiable data "how much time" and "how many times", so that the unquantifiable "delicious" appears more often, and then slowly and finely adjust the "coffee powder content" and "grinding thickness". In the end, you will adjust the "damping factor" and "porosity" very well and stably. At the same time, there is always a "delicious" Espresso, which is always appreciated by you and others. This is the art of cooking Espresso.

In addition, I have a personal suggestion: you can use the "weight meter" to practice the stress you are used to. Whether it's 7 kg, 10 kg or 15 kg, it's fine! But you have to be "stable". As long as you practice steadily, "coffee powder" and "grinding thickness" will help you achieve a certain "damping factor". You don't have to follow anyone's advice, it has to be 20 pounds, 30 pounds. Unless you can drink it and fill in the difference between 20 pounds and 30 pounds of coffee, you don't have to follow it.

In addition, there is a "doubt", which is still "bitter" to this day! I really can't drink it: the difference between using "stainless steel filler" and "acrylic filler"?! "copper filler" is not good. I can accept this argument because copper will rust. But my tongue can't tell the difference between the coffee brewed with "stainless steel filler" and "acrylic filler". So I have a little self-abasement, but honestly admit: I think they "have no difference"!