The principle of Italian espresso extraction: on the effect of coffee powder on concentrated extraction

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The concentrated extraction flow is completely different from the boiling extraction flow, because the concentrated extraction is carried out by pressure and resistance. The pressurized extraction water touches the upper end of the powder bowl, and the flow of water through the solid coffee pressed powder creates resistance, thus creating pressure throughout the coffee pressed powder field.

An important factor in this resistance is the particle size distribution (grind distribution) of coffee powder. The particle size distribution of coffee powder makes the resistance layer of coffee pressed powder, and various coffee ingredients can be extracted by pressure.

These coffee powders are made up of particles of different sizes to produce extraction resistance. The one who has made the greatest contribution to this process is Fine.

Micropowder refers to very small coffee particles, usually less than 100 centimeters (microns).

| | Conceptual map of coffee pressed powder structure according to particle size |

These fine particles were once seen as limiting the extraction speed between thicker particles and helping to make a more stable extraction flow.

However, recent studies have pointed out that the fine powder not only affects the flow rate, but also has a direct effect on the whole extraction. Because micro-powder accounts for a large proportion of the extracted coffee powder.

Generally speaking, 70% of the coffee powder is 80% of the so-called micro powder.

The following chart shows the particle size distribution (volume) and surface area benchmark particle size distribution of tapered blades (ROBUR) and flat blades (ANFIM SUPER CAIMANO).

The above data should let us seriously consider the effect of particles on extraction.

In summary, coffee particles make a stable flow and extraction, while producing a surface area that is effective for extraction.

Before we just talk about the uniformity of particles, we need to understand the kinetics and principle of coffee extraction.