Why Bloom in Pour-Over Coffee | How to Judge Coffee Bloom Situation | How Long Should Bloom Time Be

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What is Coffee Blooming?

The so-called blooming is a pre-treatment step that involves wetting the coffee grounds with a small amount of hot water before the actual brewing process begins. After roasting, coffee beans gradually release carbon dioxide through small pores on their surface, a process known as degassing or maturation. The release rate varies depending on the roasting degree, and slows down over time. 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 being ground into coffee powder, the surface area in contact with the outside world increases dramatically, and gases begin to escape. These gases form a barrier layer between the hot water and the powder, preventing effective extraction. Additionally, when carbon dioxide dissolves in water, it creates an acidic taste that results in unpleasant mouthfeel. Wetting causes the temperature to rise, forcing gases upward and making the surface of the coffee powder bulge and expand overall. Some people say that the degree of bulging on the coffee powder's surface represents the coffee's freshness, but regardless of whether it forms or its size, the key is whether this action achieves its purpose.

The importance of blooming lies in first releasing the gases that would interfere with pour-over extraction, making the extraction process smoother.

In addition to degassing, as the gases escape, hot water also fills the voids. The contact between the powder and hot water releases aromas. Furthermore, the powder expands after absorbing water, creating space between particles. The circulating gases promote expansion, opening up pores between the powder particles, making it easier for water to pass through. This helps with subsequent water flow control - all of these are side effects of gas release.

Two Purposes of Blooming

There are two purposes of blooming:

First:

To release gases from the coffee particles, primarily carbon dioxide. Generally, the closer to the roasting time, the more bubbling occurs during pre-infusion. Darker roasted coffee beans, having less moisture content, also release more gases during the blooming process than lighter roasted coffee beans.

Second:

After the gases are released, if the coffee particles can absorb water and become saturated evenly, it allows for more uniform subsequent extraction. In short, during blooming, the air between coffee powder particles expands due to heat, releasing large amounts of carbon dioxide. A temporary gap layer appears between the coffee powder particles, providing the necessary space for hot water to pass through the powder layer during the actual pouring process.

Now you know why pour-over coffee needs blooming!

FrontStreet Coffee wants to tell everyone that blooming isn't just about blindly waiting for time to pass! It should be adjusted according to the freshness of the beans. The fresher the beans, the longer the blooming time can be; the longer the beans have been roasted, the shorter the blooming time can be, or even skipped entirely!

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473