Does Pour-Over Coffee Blooming Really Need 30 Seconds? What Affects Coffee's Carbon Dioxide Content?

The Art of Pour-Over Coffee: Understanding the Bloom

There are numerous methods for brewing pour-over coffee, but it can be said that the vast majority of brewing processes mainly consist of two steps: blooming and extraction.

Although both involve extracting coffee grounds with hot water, in pour-over brewing, the blooming step serves more as a preparatory stage. By using a small amount of hot water to moisten the coffee grounds, carbon dioxide within the grounds is released, and through capillary action, connections are established between coffee particles. This allows subsequent hot water to not only extract more efficiently but also distribute more evenly. Therefore, we can understand that the blooming step is crucial for making pour-over coffee.

However, traditionally, most coffee professionals have been accustomed to using a standard time for blooming: 30 seconds. Little do they realize that not all coffee beans require 30 seconds of blooming. Of course, FrontStreet Coffee is not saying this time is wrong, but if you want to make more delicious pour-over coffee, we cannot be limited to fixed formulas. Beans will have different blooming time requirements based on their own condition changes. Only by using the right time can we create better-tasting pour-over coffee!

So, to make better pour-over coffee, we first need to achieve a "perfect bloom"! And the first step to a perfect bloom is knowing how to determine when the blooming should end!

How to Determine When Blooming Ends

After all, the main purpose of blooming is to release carbon dioxide from the coffee beans, reducing its impact on subsequent hot water extraction. Therefore, we need to decide the blooming time based on the amount of "gas content" in the coffee beans themselves. When coffee beans contain more carbon dioxide, we need to appropriately extend the blooming time to allow the beans to release more gas. Generally, extending by about 5-10 seconds based on the 30-second blooming time is sufficient.

There are mainly two types of coffee beans that require extended blooming time: freshly roasted coffee beans within their degassing period. Because they are too fresh, they haven't had enough time to release the carbon dioxide "filled" during the roasting process, so when brewing, we need to appropriately extend the blooming time.

Secondly, high-density coffee beans (light roast) have low expansion rates, so there aren't many gaps for carbon dioxide to flow through. Fewer gaps mean the gas release speed will slow down. Therefore, although their carbon dioxide content isn't high, they need more time to release the carbon dioxide that affects extraction. Both the degassing time and blooming time need to be relatively extended.

When there isn't much carbon dioxide left in the coffee beans, there's no need to waste too much time on blooming, so at this point, we can appropriately reduce the blooming time, shortening the extraction duration (by 5-10 seconds). These include:

Beans that have been stored for a long time after roasting. Because they've had ample time to release gas during storage, there's little carbon dioxide left inside when brewing, so they don't need extended blooming time for degassing! Secondly, dark roast coffee beans, although they undergo a longer roasting process resulting in more carbon dioxide, have higher expansion rates, making them more "sensitive." When they encounter hot water, carbon dioxide rushes out at once. After the degassing period, they don't need excessive blooming time for gas release!

Achieving Perfect Blooming Technique

However, sometimes information cannot be fully seen before brewing! Therefore, we still need to determine the timing based on the condition of the coffee bed during blooming. So, the first thing to do is to evenly moisten the coffee bed, which is also the second key point of perfect blooming! If you cannot evenly moisten the coffee bed, then the blooming step loses its main significance.

So, how do you evenly moisten all coffee grounds with a small amount of hot water? It's simple—distribute the hot water according to the distribution of the coffee grounds! If you're using a conical dripper, you can focus the small amount of hot water for blooming on the center. For example, using a very small water flow to pour from the center outward in a circular motion, but spending more time/adding more water in the center!

Alternatively, you can pour in circles from outside to inside. Either way, the main focus of pouring should be concentrated on the center position where the coffee grounds are most densely packed! The same principle applies to trapezoidal drippers. If you're using a cake/flat-bottom dripper, we just need to keep the coffee bed level and pour water evenly in a circular motion.

After the water has evenly moistened the coffee bed, we can observe the degassing state of the bed! There are two things to observe: the moisture level of the coffee bed and the frequency of gas release. If we see the coffee bed has dried up before 30 seconds of blooming time, with no fresh bubbles appearing, it indicates that this coffee bean has little carbon dioxide left and no longer needs continued blooming— we can start the next stage of pouring;

However, if after 30 seconds, the coffee bed remains moist and bubbles are continuously emerging, it indicates that there's still a large amount of carbon dioxide inside the coffee grounds. At this point, we can appropriately increase the blooming time to allow the bed to release more "obstructions"~

Therefore, we can understand that as long as the blooming time matches the current state of the beans, it can make the subsequent extraction more optimal. Calling it a perfect bloom would not be an exaggeration~

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