A brief discussion on the principle of espresso extraction to analyze the extraction time and operation sequence of espresso

With the vigorous development of Italian milk coffee today, the taste and taste of espresso also highlight its position. espresso is the cornerstone of a cup of coffee, and its quality and taste are directly related to the quality of a cup of coffee! At the International WBC Barista Competition, espresso production is also an important competition point. Coffee industry insiders and coffee lovers all over the world will lock their eyes on this golden liquid with only 30cc. From this, its importance can be seen!

Perhaps my analysis is relatively shallow, please forgive me, this is also a little experience during my work!

As we all know, espresso is quickly extracted by high-pressure water through nine atmospheres of pressure, so the requirement for extraction is to stabilize the flow rate, and to control the extraction time in about 25 seconds, so that the coffee taste will be balanced. Only by allowing the water to penetrate the coffee powder evenly can the flow rate be stabilized.

Therefore, the first requirement is to press the powder horizontally, and evenly, do not appear skewed phenomenon, so that all parts of the coffee powder surface are subject to equal pressure.

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

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

First of all, let's talk about popular powder and filling pressure. Most of the data given on the Internet or books are (single serving)7 grams of powder, 15-20 kilograms of filling pressure. The operation method is to directly fill the powder, fill it flush with the edge of the handle, scrape the powder with the top cover of the bean grinder at an angle of 45 degrees, fill it, put it on the machine, and extract it.(Fresh coffee beans under normal temperature and humidity environment) is very fine for the first ten seconds, relatively stable, dark brown liquid, twelve seconds flow suddenly thick and accelerate the flow rate, fifteen seconds or so 30cc. Such a cup of esptesso is not qualified, the early extraction will be excessive, the burnt smell is quite obvious, the late extraction is unstable, the taste is messy, the oil is less, and even the extreme bitter taste appears. Such a cup of coffee can be regarded as miscellaneous taste complete!

Many people think that it is not enough pressure powder strength, powder cake broken caused. If we carefully analyze what happens in the handle when espresso is extracted, I believe you will reconsider whether you should only work on the pressure of the powder!

As we all know, there are many factors that affect espresso. My analysis means that in general, don't dwell on details.

First of all, let's talk about what happened in the coffee handle. After pressing powder, due to the coffee powder is solid, water will accumulate in the gap between the brewing head and the coffee powder surface, resulting in too fine extraction flow rate in the early stage, resulting in excessive extraction. When hot water penetrates the coffee powder, the coffee powder will automatically expand, and the powder position will begin to rise. After a certain degree of expansion, there will be a large uneven gap between the coffee powder particles inside the coffee handle. Hot water will penetrate the coffee powder instantly in such a gap, resulting in insufficient extraction in the later stage.

Therefore, under such analysis, you will realize that the extraction of espresso is not completely determined by the pressure of the powder to determine its flow rate and state, 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, the gap after expansion is uniform, and the water will be stable. Uniform penetration of coffee powder, uniform extraction, control of extraction time. Since the origin of the name espresso is related to pressure, I think it should refer to the water pressure of the coffee machine and the pressure of the whole extraction inside the coffee machine handle, so we should comprehensively consider the water and coffee powder inside the entire handle and the expansion space, do not simply consider the pressure on the surface of the coffee powder, understand such changes and principles can adjust their grinding degree and pressure powder strength and extraction time.

PS: Of course, this is an analysis of the overall extraction principle. There are still many problems in the details of each restaurant, including the brand, performance, water pressure, etc. of the coffee machine. Please don't dwell on these problems. I emphasize the overall principle analysis, so if you have any better suggestions, please don't hesitate to give me advice! thank

Source: Happy Coffee Xiao Xu Blog