The coffee grinder itself does not directly control the pressure, but the grinding degree and the pressure of the coffee machine jointly affect the extraction. The following is a specific analysis:
The correlation between grinding degree and pressure
The influence of grinding degree on extraction pressure: The finer the grinding degree, the greater the density of the coffee powder cake, and the greater the resistance when water flows through, thus requiring a higher pressure to complete the extraction. Conversely, the coarser the grinding degree, the lower the density of the coffee powder cake, the smaller the resistance when water flows through, and the corresponding extraction pressure required is also reduced.
The influence of pressure on extraction efficiency: Pressure is one of the key factors in the extraction process of espresso. Appropriate pressure can ensure that water fully penetrates the coffee powder and extract the flavor substances in the coffee. If the pressure is too low, the extraction efficiency will decrease, resulting in a weak taste of coffee. If the pressure is too high, it may lead to over-extraction, making the coffee bitter.
The coordination of pressure and grinding degree under the ideal extraction state
Ideal extraction pressure range: For espresso, the ideal extraction pressure is usually between 9 and 12bar. When the real-time extraction pressure remains within this range, the flow rate of the coffee liquid is continuous and stable, presenting a fine line state. This is the most ideal extraction state.
Adjustment of grinding degree: To achieve the ideal extraction pressure, the grinding degree needs to be adjusted according to the characteristics of the coffee beans and personal taste preferences. If the extraction pressure is too high, it may be necessary to coarse the grinding degree to reduce the density and resistance of the powder cake. Conversely, if the extraction pressure is too low, the grinding degree needs to be refined to increase the density and resistance of the powder cake.
The balance between pressure control and extraction quality
Avoid insufficient or excessive extraction: When the real-time extraction pressure is 5bar, the coffee droplet speed is extremely fast, and the contact time between water and coffee grounds is insufficient, which may lead to insufficient extraction. However, if the real-time extraction pressure reaches 15bar, the flow rate of the coffee liquid will be too slow, and the contact time between water and coffee grounds will be too long, which may lead to excessive extraction. Therefore, it is necessary to find the balance point between insufficient and excessive extraction by adjusting the grinding degree and pressure.
Consider other influencing factors: In addition to grinding degree and pressure, the extraction quality is also affected by multiple factors such as water temperature, powder content, and extraction time. Therefore, while adjusting the grinding degree and pressure, the combined influence of these factors also needs to be taken into account.