How to diagnose espresso extraction (part I)

Italian 4m (barista, bean grinder, blending, and espresso machine) includes the key factors in the formation of espresso. The questions often asked on home-barista.com forums often focus on the last factor: which Italian machine should I buy? Once a buyer limits their list to a few options, family coffee makers often begin to doubt their skills and the ideal brewing temperature. My previous article, How I Stopped Worrying and Learned to Love HXs, pointed out how to find better temperature control for cooking.

If you put aside the importance of the espresso machine-- in fact, it was the search for comments on the device that led most readers to this forum-- I think the other three elements are as important as this one, or even more important. At the top of my list is the contribution of baristas. Not only do baristas have to choose these elements carefully, but also because of the skills they need to master. How good the barista's skill is, just take a look at the extraction for half a minute, and then look at the performance in the final cup.

Thank you for the help of bottomless handle for abnormal espresso extraction last year. Inspired by Chris Tacy's diagnostic series (Training with the Naked Portafilter), I started my own case study.

Join me and take a look at what happens under the Italian machine. Before we skip to the espresso extraction for diagnosing errors, let's do a brief review.

What does the barista like to observe?

A clever barista will concentrate on observing the emission of espresso during the extraction process. Although the performance at this time can not be used as evidence of the performance in the last cup, it is a good tool to verify the baristas' skills. It takes a few words to describe what the barista sees, some of which, with permission, are excerpted from Mark Prince's Espresso Glossary.

[attachment=7036]

Golden londing) indicates that the gushing color changes from dark brown and tiger spots to a lighter, evenly white color. This usually occurs at the end of the extraction of 1max 3, which is a sign of the end of cooking. At this time, the extracted espresso is thin and almost without aroma. If we continue the extraction, it will dilute the extraction which was originally enjoyed very much. 、

Channeling is a fast channel formed by cracks in coffee cakes, which results in thin, underextracted espresso. When channeling occurs, you will often see sudden blond stripes in the espresso stream. Sometimes holes the size of pencil refills are even found where channeling appears in coffee cakes.

Crema is one of the definitive signals of correctly extracted espresso (in machines without crema intensifiers), which is caused by the dispersion of gases (air and carbon dioxide) at high pressure. The liquid contains emulsified oil, forming a dark brown layer on top of the espresso.

Extraction is the process of forcing hot water in a boiler to pass through ground coffee powder, which extracts flavor, oil, colloids, lipids and other ingredients from coffee powder.

The Golden Rule is a general phrase used to describe the ideal extraction time and espresso volume. Instituto Nationale Espresso Italiano (PDF) provides an ideal working definition of espresso. The simplified definition of my own espresso is to use about 14 grams of coffee and extract 60 milliliters of coffee in 22 to 32 seconds (timing from the start of the pump).

Excessive extraction occurs when too much coffee is extracted, resulting in a cup of coffee with a strong and rough flavor. Visual information is to extract a small amount of coffee, the color is dark, crema is very thin. The dark "halo" on the edge of the cup is another typical sign of over-extraction, or that the extraction water is too hot.

Pre-soaking: the act of soaking the coffee pressed powder in the coffee machine before starting the formal extraction. Some coffee machines use a pump to do this: the water is pumped to the coffee for 1 to 2 seconds, and then stops for 1 to 2 seconds. After this pause, the pump works again until the cooking is finished. Super fully automatic and some fully automatic machines use this prepreg method.

Another kind of prepreg is called "natural presoaking" or progressive prepreg, which is used in machines equipped with E61 cooking heads. When the pump starts working, a chamber needs to be filled before pressure is applied to the coffee cake. This allows 3 to 7 seconds of infiltration before the pressure is established. This kind of prepreg is better than the previous method of "turn on the pump-pause-open the pump".

Tiger pattern and tiger spot are the most important visual features of good extraction. The tiger pattern is formed by the contrast of dark crema and light crema; ideally, it appears in the early stages of cooking and continues until the end of cooking. Tiger spot is confirmed in the cup with good extraction; it is a small dark brown or dark red spot floating on the surface of Crema.

Underextraction occurs when too little coffee is extracted. Lack of extraction will result in a weak cup of coffee with a dark flavor. The visual representation of underextraction is a bright golden crema.

This is the end of the noun explanation, and we can now begin to understand how to identify the correct extraction-and bottomless cooking handles can make it obvious! The above is an example of using Cimbali Junior DT1 extraction, which shows a great tiger pattern. The colors are evenly distributed and are continuous throughout the gushing process.

The Golden Rule of Espresso

As mentioned in the mini-noun list above, the golden rule of an ideal espresso indicates the extraction time and amount. The golden rule is a good guideline, but in many cases, color is a better indicator of grinding thickness and whether the packing is correct or not.

Although it is not absolutely necessary, the extraction process can be clearly shown by observing the extraction with a bottomless cooking handle. When using a "normal" cooking handle, you can also get a lot of symptoms by carefully observing the flow from the diversion head. Color can give you a clear signal of when to stop the extraction, and remember that the tiger grain will fade with the time the beans are placed. Also remember that decaffeinated coffee has very small stripes; decaf beans tend to be darker and more uniform at first and turn golden earlier than caffeinated beans. Of course, the stripes of freshly baked beans are darker when they are cooked. Depending on the formula of the mixed beans, you will get the best results four to ten days after baking.

Although stopping extraction when golden yellow appears will get you a cup of the best espresso, correcting inappropriate extraction itself can lead you to a better espresso. If the extraction is too slow, the espresso will be more bitter and the dark brown crema;. If the extraction is too fast, the espresso tends to turn sour and the crema will all turn cinnamon. Tasting is the ultimate guide to correct all kinds of mistakes (grinding, packing, and temperature). Keep practicing and get good cooking is basically a skill.

Divide the material, powder, fill and press. Repetition

Let's assume that the cooking pressure of your espresso machine has been adjusted correctly and the cooking temperature is correct. I suggest setting the cooking pressure to 82. When you get to 9.5bar, set the cooking temperature to 202 degrees Fahrenheit as a good starting point. Suppose you have chosen a good coffee mill and fresh espresso mixed beans, and now the final result depends on the extraction. Within 25 seconds of boiling a cup of espresso, a lot can happen. If you have a standard cooking handle, your observation is limited to the flow of water in the water divider. The bottomless cooking handle provides a new and favorable perspective for this process.

Before entering into the common extraction defects, I will briefly talk about how to correctly prepare the coffee to be extracted. Basically based on the skills mentioned in his article Espresso Packing Techniques: Update 2004 by the owner of David Schomer,Vivance, an influential barista trainer. The first page of the online article is a step-by-step reference card, and the scanned text is more difficult to read, so I excerpt part of it below, starting with the third picture:

3. There is a small pile of freshly ground coffee in the powder bowl

4. After filling up all the lows, push the coffee towards 12:00

5. Now, at the top, push the coffee with your fingers toward six o'clock.

6. Push the extra coffee to the middle of the powder bowl and repeat the above steps

7. Under a pressure of 40 pounds. Turn and flatten when lifting the powder press

8. Gently side-tap; notice that the cooking head is lifted from the table.

9. Using bathroom scales to train operators can use 40 pounds of pressure powder.

10. When finished, press down with 20 pounds of pressure and turn the powder press clockwise to smooth the coffee powder.

Using the above steps as guidelines, let's review the distribution, distribution, and packing in a little more detail.

Ingredients: baristas in business need to make espresso cup after cup. Almost all professional baristas grind one batch of powder at a time. The techniques they use to ensure the same amount of powder each time may vary, but the error of each powder should be 0.5g or less.

The production speed required by a typical family barista is not high, and the dispensing skills can be adjusted more consistently. Some family baristas choose to throw only a small amount of beans at a time, weigh out a fixed amount of beans, then grind the beans until the grinder is completely polished, and then clean the divider. This eliminates the waste of coffee, but it also brings a lot of extra work. In addition, if you have a hobby of analysis, and you also happen to have a high-precision scale on hand, weighing can help you ensure the consistency of each distribution, especially when you are a beginner. When I'm in the "exploration phase" of an espresso machine, I often call it beans every time, and when I'm already comfortable with the machine, I use a lot of ingredients instead. This saves coffee and eliminates the source of variables for each extraction.

No matter which way you use, keep in mind that the thickness of pressed powder is more important than the accuracy of weight. If the pressed powder is too high in the filter bowl, it will be cut to the top of the pressed powder during the lock of the handle to the head, especially on the right-hand side. This results in the side channeling shown in the first image in Hall of Shame.

The weight of the double filter bowl standard on most espresso machines is about 14g. That is to say, if you fill it with the same method each time and fill it with the same level of powder, you will get almost accurate 14g coffee. If you follow the above method, there will be nearly 16g of coffee in the filter bowl. This is why it is called the "overfeeding" filter bowl. The optimal weight will vary depending on the setting of the bean grinder, the beans, and the type of mill.

It is important to leave a gap between the showerhead and the top of the pressed powder. It also allows water to be distributed on the surface of pressed powder and allows pressed powder to absorb water and expand to come into contact with the showerhead. In the case of maximum loading, if you put a coin (2mm thick) on the general side of the pressed powder, the coin should just touch the showerhead when the handle is locked. However, it is important to keep in mind that if pressed powder is crushed while locking, side channeling will occur.

Distribution: when uneven extraction is caused by inconsistent packing pressure, we all blame the packing pressure. But in fact, in most cases, the error is incorrect distribution.

I prefer to overfeed in a slightly different way from the steps described by David Schomer. Unlike his overfed filling method, I would tap the cooking handle on the fork of the bean grinder twice when the filter bowl was full, and then fill the bowl. Finally, I did four unpressurized leveling movements: South-North, North-South, West-East, East-West.

The method I recommend will be easier to ensure consistency than other methods you may read on the Internet. Consistency is the key to continuous improvement and the ability to judge when something goes wrong all the time. Ignoring some small steps in your process will add variables unnoticed. For example, in a recent barista contest, I saw some contestants side-tap the handle once to shake off the powder in their first brew, and four times in the second brew, followed by a final addition of powder. Finely ground coffee powder will sag slightly with each side hit, so these contestants may have a change of 1g or 2g in each cooking, which can increase or decrease the cooking time by several seconds.

Filling pressure: the purpose of filling pressure is to improve the density consistency of coffee pressed powder. If the pressure is not filled, the high pressure in the extraction process will create a crack in pressed powder. In the earlier definition, pressurized water was called channeling through these cracks, so instead of extracting coffee evenly through pressed powder, the water quickly passed through the cracks, extracting only the coffee powder on the edge of the channel. The resulting coffee will be very similar to the golden part of the coffee when it is normally extracted, thin, almost without aroma, and not sweet.

Hold the powder press like a doorknob, that is, keep the shaft in the palm of your hand along the length of your hand. Professional baristas generally recommend adding 30 to 40 pounds of stress. This is also a good guideline for family baristas, but again, consistency should be your top consideration. Consider using a training powder press such as Espro, which is calibrated to a pressure of 30 pounds, or using a scale in an inexpensive bathroom to train yourself to achieve stable pressure.

My reference is a packing method called "Staub", which was created by Carl Staub. Staub fills the coffee that focuses on the edge of the powder bowl. This filling method is first filled and pressed once in the center of the powder bowl, then pressed again in the direction of the four corners of the compass, lifting the powder press each time, and finally gently pressed and smoothed out. There is not a large gap between the edge of the powder press and the filter, so it is a bit of a mistake to say that you are filling the "edge". Professionals are usually faced with long queues of customers who are in a hurry and don't have time to take so many steps. But for me, it was worth the time to make sure pressed powder was pressed all around in order to get a great espresso.

(the information is from the Internet. I have slightly modified it for sharing reference only. if the editor of this article does not agree to share, please contact me to delete it.)