How to Brew Delicious Coffee: A Liberal Arts Guide to Understanding Pour-Over Coffee and Segmental Extraction Principles

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FrontStreet Coffee - Pour-Over Coffee Extraction Introduction

The first stage of pour-over coffee is called pre-infusion or blooming. First, pour a small amount of hot water to moisten the coffee grounds, then wait for about 30 seconds. The purpose of this is to expel carbon dioxide.

When coffee beans are roasted, gases are trapped inside the beans. After roasting, the coffee slowly releases gas, and it also releases gas during brewing. When the coffee grounds come into contact with hot water, the remaining gas is released, and this process is called blooming. The more gas released, the greater the expansion of the bloom.

Blooming helps develop coffee flavor in two main ways: First, carbon dioxide itself has a sharp, sour taste, and this flavor is not pleasant when mixed into coffee (the sourness mentioned here is different from fruit acidity and vibrant acidity).

Second, when coffee grounds release gas, the gas interferes with the contact between coffee grounds and water, affecting the extraction process. You want this process to occur during the pre-infusion blooming stage rather than in the later extraction process. Pre-infusion can reduce inconsistencies in the extracted flavor.

2. Extraction

The next stage of pour-over coffee is to begin controlling the flavor of the brewed coffee. Different stages of brewing extract different chemical compounds. First, the fruity acidity from the coffee is extracted, followed by sweetness, and finally bitterness (but it's worth noting that not all acids are as pleasant as fruit acidity; for example, chlorogenic acid produces astringency, dryness, and bitterness. In this article, we only focus on acids that produce positive acidity).

Since different time points during pour-over brewing extract different chemical compounds from coffee, you can create your preferred coffee flavor by adjusting brewing techniques. The best way is to control water temperature and brewing time. Generally, the ideal pour-over temperature is about 90-96 degrees Celsius. Depending on the roast degree, flavor characteristics, solubility, bean freshness, and grind size, each has its corresponding optimal water temperature.

An important aspect of this stage is water interruption, where the brewer divides the water into multiple pours. For pour-over coffee, some suggest reducing the number of water interruptions to increase the stability of each brew, which eliminates human bias caused by the barista.

Water interruption is very important because it can bring more stable and efficient extraction. Because larger water flow and fewer pours shorten the extraction time, while using smaller water flow for multiple pours can make the coffee bed flatter. The number of water interruptions varies depending on the nature of the coffee and grind size.

3. Finishing

The finishing stage of pour-over coffee is defined here as the brewing of the final 40% of water volume. Patrik mentions that this part should be controlled carefully because the final stage of extraction can easily release bitterness and other unpleasant flavors from the coffee. Even if the earlier stages are done well, this cup of coffee can be ruined by over-extraction at the end.

It is recommended to carefully adjust brewing time and water temperature. The finishing stage may extract fewer compounds due to decreased water temperature. Similarly, if you can master the water temperature during this stage, you can create a coffee with good balance, sweetness, and acidity.

For pour-over brewing, water temperature will naturally decrease, but if using a coffee machine or pour-over machine, you might be able to set staged water temperatures. It is recommended to set different brewing parameters for different coffees, as water temperature remains key to affecting coffee sweetness, fruit aroma, and balance.

Knowledge Point

This method creates richer layers than a single pour, clearly distinguishing the front, middle, and back-end flavors of the coffee. The approach is to increase the amount of water poured each time after blooming, typically pouring when the coffee liquid is about to drop to the surface of the coffee bed, using small, medium, and large water flows for three-stage extraction.

In Summary

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