What is the Purpose of Pour-Over Coffee Blooming? Key Factors Affecting Pour-Over Coffee Blooming

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FrontStreet Coffee - Introduction to the Purpose of Pour-Over Coffee Bloom

Do you truly understand the significance of this process?

Pour-over coffee is a process where flavor extraction and filtration occur simultaneously, centered around where water is poured—the more water, the more extraction. Freshly roasted coffee beans produce more carbon dioxide, which prevents water from fully contacting the coffee grounds for complete extraction. Therefore, blooming is necessary to avoid uneven coffee extraction and reduced efficiency.

Bloom, the so-called blooming process, is a preliminary step in which a small amount of hot water is used to wet the coffee grounds before the actual brewing begins. After roasting, coffee beans gradually release carbon dioxide through small surface pores, a process known as "waking the beans" or maturation, with emission rates varying depending on the degree of roast. As time passes, degassing slows down, and blooming captures the moment when hot water contacts the powder, allowing gases to escape quickly.

This seemingly simple action significantly affects the final product. After grinding into coffee powder, the surface area exposed to the outside world greatly increases, and gases begin to escape. These gases form an isolation layer between hot water and the powder, preventing effective extraction. Additionally, when carbon dioxide dissolves in water, it produces a sour taste, resulting in unpleasant flavors. Wetting allows the temperature to rise, causing gases to escape upward, making the surface of the coffee grounds swell and expand overall. Some say that the degree of swelling on the coffee grounds' surface represents the coffee's freshness, but regardless of whether swelling occurs or its magnitude, the key is whether this action achieves its purpose.

Typically, blooming time is 20-30 seconds. Once blooming ends, hot water should be immediately poured. The endpoint for judging completion is when the coffee grounds are at their maximum expansion, before they collapse. If you have a scale, you can pour hot water weighing twice the amount of coffee grounds, or simply use a small amount of water to slightly moisten the coffee grounds.

Blooming brings two positive effects to coffee flavor:

First, carbon dioxide has a sour taste. If not released during blooming, it will make the coffee taste unpleasantly sour.

Second, carbon dioxide blocks contact between water and coffee. Only by releasing carbon dioxide can coffee's aromatic compounds and oils be more completely dissolved.

As long as coffee grounds still contain gas, they will interfere with water's ability to extract substances from the coffee, and will make the extracted coffee have a stimulating sour taste.

Next time when you make pour-over coffee yourself, remember to bloom first, allowing the coffee to breathe to capture its charming flavors, while avoiding negative flavors and sourness caused by carbon dioxide.

Knowledge Extension

In the world of pour-over coffee, restoring the bean's flavor as much as possible and making it delicious is most important. Every step toward achieving this goal can be full of creativity, so there are many brewing techniques—what we often call different pour-over schools or styles.

In summary: FrontStreet Coffee is a coffee research workshop that enjoys sharing coffee knowledge with everyone. We share without reservation to help more friends fall in love with coffee. Additionally, we hold three coffee events with low discounts each month, because FrontStreet Coffee wants to let more friends enjoy the best coffee at the lowest price. This has been FrontStreet Coffee's mission for the past six years!

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