Should Pour-Over Coffee Blooming Time Be Counted from the Start or End of Water Pouring? Is Blooming Considered a Separate Phase in Coffee Brewing?

"So first, we pour twice the amount of water as the coffee grounds for a thirty-second bloom."

This is a step that FrontStreet Coffee always performs at the beginning of brewing—the bloom. Under normal circumstances, this step is always present in the brewing process because blooming makes it easier for us to brew a delicious cup of coffee.

Many friends have actually been quite curious about why the blooming time must be 30 seconds and why it must use twice the amount of water as the coffee grounds. Would it not work if the time is a bit longer or shorter, or if the water amount is a bit more or less?

Of course, it can! The time and water amount used for blooming are not actually required to be limited to any specific standard—we can certainly freely control these values. However, before changing parameters, we need to understand what the purpose of blooming is, and why these two values are recommended, so that we can know when to adjust the time and when to adjust the water amount.

The First Purpose of Blooming: Degassing

As everyone knows, the primary purpose of blooming is to allow the coffee grounds to degas! After coffee beans are roasted, large amounts of carbon dioxide accumulate within them. This carbon dioxide has both benefits and drawbacks: the benefit is that it can slow down the loss of coffee flavor compounds, extending the flavor period of the coffee beans; the drawback is that during brewing, the presence of carbon dioxide hinders hot water from extracting flavor compounds. It acts like a wall, blocking external access to these flavor compounds.

If we brew directly without degassing when the beans are relatively fresh, the hot water will be obstructed by carbon dioxide, resulting in lower extraction of compounds. FrontStreet Coffee conducted a special experiment using the same beans with the same extraction parameters (brewing time controlled at two minutes), with the only difference being whether blooming was performed.

The extraction rate of the coffee without blooming was 13.53%, while the extraction rate of the bloomed coffee was 17%. From this, we can see how significant the impact of carbon dioxide on extraction is. Therefore, we need to use the blooming step to release the carbon dioxide from the coffee grounds that hinders extraction. So why do we need to use 30 seconds for blooming?

There's actually no strict requirement for blooming to be exactly 30 seconds—25 or 35 seconds would also work. However, 30 seconds has relatively broader applicability, allowing for relatively sufficient degassing regardless of the age of the coffee beans. If the blooming time is less than 30 seconds, for some fresher coffee beans, degassing might be insufficient due to excessive gas, which would affect extraction; if it exceeds 30 seconds, although the coffee grounds will continue to degas, the effect won't be as good, and the degassing speed will slow down significantly. Therefore, 30 seconds is a relatively safe degassing time that neither results in insufficient degassing nor wastes too much time on blooming.

So in what situations should we use other blooming times? It's simple: when carbon dioxide content is either too high or too low. If coffee beans are too fresh with very high carbon dioxide content, 30 seconds might not be sufficient for the coffee grounds to degas thoroughly. Therefore, we can appropriately extend the time by about 5 seconds to allow more carbon dioxide to be released from the coffee grounds, so the subsequently poured hot water can better dissolve the coffee's flavor compounds. When coffee beans are no longer that fresh and carbon dioxide content has decreased, we don't need to use excessive time for blooming—we can directly reduce the blooming time based on the moisture state of the coffee bed (about 5 seconds).

The Second Purpose of Blooming: Saturation

The second purpose of blooming is to saturate the coffee grounds, creating connections between grounds and reducing uneven extraction caused by channeling during subsequent extraction. But we all know that the main purpose of blooming is to degas, paving the way for subsequent extraction. Therefore, if too much hot water is used for saturation at this stage, the compounds extracted by this portion of water will be relatively less compared to what would be extracted if it were used during the main extraction phase.

Because the coffee grounds haven't undergone degassing yet, hot water cannot extract effectively. Therefore, we need to minimize the amount of water used during blooming. However, endlessly reducing it will prevent the coffee grounds from being fully saturated, especially those at the bottom of the filter cup. So, our requirement for blooming water amount is: less, but not too little. Coincidentally, dry coffee grounds will absorb a certain amount of water, so people thought of using this amount of water for blooming, which can effectively reduce hot water waste while ensuring the coffee grounds are fully saturated.

Just like time, the blooming water amount is also just a relatively reasonable parameter that isn't fixed—we can adjust it based on the condition of the beans! However, there's no need to deliberately adjust it, because the water amount used for blooming is actually quite appropriate. Unless you're a complete beginner who can't fully saturate the coffee grounds in the filter cup with this small amount of water due to insufficient technique, then we can appropriately increase the blooming water amount by about 10ml~

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