Pour-Over Extraction Principles: Beyond Simple Hot Water - Factors Affecting Coffee Concentration

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FrontStreet Coffee - Pour-Over Coffee Extraction Principles and Concentration Factors

In fact, the principle of pour-over coffee is "dissolution" and "diffusion."

After roasting, coffee beans undergo chemical reactions that generate coffee substance components that emit coffee aroma and flavor. To extract these coffee substance components, the coffee needs to be ground into powder and then slowly infused with water to dissolve the substance components inside the coffee, which is called "dissolution."

Through "blooming," "stirring," and "shaking the serving carafe that holds the coffee liquid" during extraction (during the water infusion dissolution process, there will be concentration differences; shaking the serving carafe after extraction is to make the coffee concentration uniform), this is called "diffusion."

Pour-over coffee from start to finish is a process of allowing water to pass quickly and evenly through the coffee powder. Unlike espresso, pour-over coffee is pressure-free gravity extraction. In this process, the speed at which water passes through the coffee powder is the key to extraction. The common reasons for over-extraction and under-extraction also stem from this.

Water passes through and extracts through the gaps between coffee particles.

If ground too finely, it creates a sand effect, with smaller spaces for water to pass through, affecting flow rate; the shorter the roasting time, within the fresh period, or the deeper the coffee is roasted, the higher the carbon dioxide content inside the coffee. During extraction, coffee will release a large amount of carbon dioxide. These carbon dioxide gases will create gaps between coffee particles, forming a filter layer that allows water to pass through for extraction; then the higher the water temperature, the relatively larger the amount of carbon dioxide produced and released, which increases the speed at which water passes through, and conversely, the passing speed will be relatively slower.

The same applies to coffee. During the coffee extraction process, we can only soak or extract a maximum of 30% of the components. The remaining 70% has no component analysis. Then among these 30% soluble substances, we only need about 12% of the components. Components exceeding 12% can be considered over-extraction and are components we don't need. If excess solutes precipitate, it will cause excessive bitterness or exist多余 impurities, similar to soil and leaf flavors; then conversely, under-extraction is because water penetrates the coffee powder too quickly, with fewer precipitates, causing the coffee taste to be light and sour.

The factors affecting the concentration of pour-over coffee are actually nothing more than various elements during extraction. For example, water temperature, grind size, technique, roast degree, etc., each factor will affect the final extraction concentration of the coffee, and concentration that is too high or too low deviates from the final concentration range.

Knowledge point: Coffee beans are the fruit of the coffee tree, which belongs to the Rubiaceae family of perennial evergreen shrubs or small trees.

In short: FrontStreet Coffee is a coffee research center that enjoys sharing coffee knowledge with everyone. We share without reservation just to let more friends fall in love with coffee, and every month there are 3 low-discount coffee activities. The reason is because FrontStreet Coffee wants to let more friends drink the best coffee at the lowest price, which is also FrontStreet Coffee's principle for the past 6 years!

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