Italian Coffee making course: a brief discussion on the details of the Analysis of espresso extraction principle

Today, with the vigorous development of Italian milk coffee, the taste and taste of espresso also highlight its status. Espresso is the cornerstone of a cup of coffee, its quality and taste are directly related to the quality of a cup of coffee! In the international WBC barista competition, the production of espresso is also an important competition point. Coffee industry insiders and coffee lovers all over the world focus on this golden liquid with only 30cc, so its importance can be seen!

Perhaps my analysis is relatively shallow, but also ask the heroes to forgive me, this is also a little bit of experience during my work!

As we all know, espresso is quickly extracted from high-pressure water through nine atmospheric pressures, so the requirement for extraction is to stabilize the flow rate, and it is necessary to control the extraction time to produce 30cc in about 25 seconds, so that the taste of the coffee will be balanced. Only by letting the water evenly pass through the coffee powder can the flow rate be stable.

So the first requirement is to press the powder horizontally and evenly, without skew, so that the pressure on all parts of the coffee powder is equal.

The second point is about the analysis of the gap between the brewing head and the coffee powder inside the handle during the extraction, which I think is the most important part in the extraction.

The two key points to be mentioned in this part are powder loading and packing.

First of all, let's talk about the popular powder and filling pressure. generally, the data given on the Internet or in books are mostly (per person) 7 grams of powder, and the filling strength of 15muri is 20 kilograms. the method of operation is to load the powder directly and keep it level with the edge of the handle. scrape the powder with a 45-degree angle with the top cover of the bean grinder, fill the pressure, get on the machine, and the extraction state (under the general temperature and humidity environment, fresh coffee beans) is very fine and stable in the first ten seconds. Liquid is dark brown, 12 seconds flow suddenly thick and speed up the flow rate, 15 seconds or so 30cc. Such a cup of esptesso is failed, the early extraction will be excessive, the scorched taste is quite obvious, the later extraction is unstable, the taste is messy, there is less oil, and even extreme bitter taste. Such a cup of coffee can be regarded as full of miscellaneous flavors!

Many people will think that it is due to the lack of powder pressing and the breaking of pressed powder. If we carefully analyze what happens in the handle of espresso extraction, I believe you will reconsider whether you should only work on the power of powder pressing!

As we all know, there are many factors that affect espresso. My analysis means that under normal circumstances, do not dwell on the details.

First of all, let's talk about what's going on in the coffee handle. In this way, after pressing the coffee powder, because the coffee powder is solid, the water will accumulate in the gap between the brewing head and the coffee powder, resulting in the early extraction flow rate is too fine, resulting in excessive extraction, and the coffee powder will automatically expand when hot water passes through the coffee powder. the position of the powder will begin to rise, resulting in a large uneven gap between the coffee powder particles inside the coffee handle after a certain degree of expansion. Hot water will instantly penetrate the coffee powder in such a gap, resulting in insufficient extraction in the later stage.

Therefore, under such analysis, you will realize that the flow rate and state of espresso are not determined entirely by the force of pressing powder. A series of reactions inside the handle show that in order to make the flow rate and extraction stable, it is necessary to ensure that the space for coffee powder expansion is reduced, and the gap after expansion is uniform, so that water can steadily and evenly pass through coffee powder to achieve uniform extraction and control the extraction time. Since the origin of the name espressso is related to pressure, I think it should refer to the water pressure of the coffee machine and the whole extraction pressure inside the handle of the coffee machine, so it is necessary to comprehensively consider the water and coffee powder and expansion space inside the handle, not just consider the pressure on the surface of coffee powder, understand this change and principle, you can adjust your grinding degree and powder pressure and extraction time.

PS: of course, this is about the analysis of the extraction principle as a whole. There are still many questions about the details of each restaurant, including the brand, performance, water pressure and so on of the coffee machine. Please don't worry about these problems. I emphasize the analysis of the whole principle, so if you have any better suggestions, don't hesitate to comment! Thank you

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Happy Coffee Xiao Xu's blog