Does Golden Mandheling Coffee Need a Blooming Step?

Pour-over coffee can be brewed without blooming, but only under specific conditions. Blooming exists to release carbon dioxide trapped in the grounds, which otherwise blocks hot water from dissolving flavor compounds and leaves the cup hollow and flat. A comparison using light-roasted Huakui and dark-roasted Golden Mandheling, brewed with identical dose, ratio and grind, showed how much extraction and flavor change when the bloom is left out.

The test used 15 g of coffee at a 1:15 ratio, ground to 85 percent passing a No. 20 sieve, so only the bloom step varied. Fresh Mandheling and other recently roasted beans hold the most gas and benefit most from blooming, while beans that have already degassed, or brews using drip, stirring or one-pour methods, may not need it. Tasting and concentration readings showed the difference.

The blooming step in pour-over coffee is a fixed ritual for many enthusiasts, but is it truly indispensable? Starting from comparative experiments at Front Street, this article provides an in-depth analysis of the core function of blooming—releasing carbon dioxide that hinders extraction—and, through brewing data from two groups, light-roasted Huakui and dark-roasted Golden Mandheling, demonstrates the significant differences in extraction yield and flavor between blooming and not blooming. At the same time, the article also explores the possibility of omitting blooming under specific conditions, such as using coffee beans that have already fully degassed, or adopting special brewing methods like the drip method, stirring method, or one-pour method. Whether you are a beginner just starting out or a seasoned player seeking a breakthrough, you can gain a clear understanding of the relationship between blooming and extraction.

The answer is yes—pour-over coffee can indeed be made without blooming. However, this "can" does not hold unconditionally; certain prerequisites must be met. Before discussing these prerequisites, it is necessary to first clarify what blooming is actually for.

The Purpose of Blooming

Front Street has emphasized many times in past articles: blooming is essentially a degassing behavior, intended to pave the way for more thorough extraction afterward. Coffee grounds often contain a large amount of carbon dioxide, and these gases create obstacles during brewing, making it difficult for hot water to effectively dissolve the flavor substances in the coffee, ultimately causing the coffee to taste hollow, flat, and lacking in layers. The following comparative experiment can illustrate this point intuitively.

The theme of Front Street's comparison this time is "the difference between blooming and not blooming in pour-over coffee." To ensure the results are comparable, both pots of coffee use exactly the same beans and brewing parameters, with the only variable being whether blooming is performed. The differences between the two are then evaluated through sensory tasting and concentration testing.

This brewing session selected two relatively fresh beans, representing different roast levels. One is a light-roasted coffee bean from the Front Street bean list—Front Street Ethiopia Huakui, and the other is a dark-roasted coffee bean from the Front Street bean list—Front Street Sumatra Golden Mandheling. The specific extraction parameters are as follows: Dose: 15g Coffee-to-water ratio: 1:15 Grind size: 85% passing rate on a No. 20 sieve Brewing time: 1 minute 50 seconds Brewing temperature: light-roasted Huakui 94°C / dark-roasted Golden Mandheling 90°C Brewing method: one-pour method Brewing process: skipped directly! Let's look at the results right away.

Huakui without blooming: The extraction yield of Huakui without blooming was 17.86%. It tasted fresh on entry, with slight fruit acidity and a light tea aroma, but the overall flavor was not prominent enough, the taste was on the weak side, and acidity dominated.

Huakui with blooming: The extraction yield of Huakui with blooming reached 19.25%. By comparison, the taste was much fuller, with distinct flavor layers. Citrus, berries, white floral notes, and oolong tea character could be clearly identified. The mouthfeel was smooth, with very good balance.

Golden Mandheling without blooming: The extraction yield of Golden Mandheling without blooming was on the low side, only 16.19%. It tasted thin, leaving only a layer of nutty flavor.

Golden Mandheling with blooming: The extraction yield of Golden Mandheling with blooming was 18.27%. The mouthfeel was noticeably richer and the flavor more prominent. Caramel sweetness, chocolate aroma, and the finish of spices and pine wood could all be clearly perceived. However, because the one-pour method was used, the body was not as strong as with a three-stage pour.

From the experimental results, it can be seen that whether dark-roasted or light-roasted, even with completely identical parameters such as beans, time, grind, and water temperature, the pot without blooming was clearly inferior in taste to the version with blooming. The extraction yield data also confirmed this difference, especially in the group with dark roasting and more abundant carbon dioxide, where the gap was even more significant. This is enough to show that under conventional brewing conditions, the importance of blooming in pour-over coffee cannot be ignored.

However, this does not mean that pour-over coffee must be bloomed. Under specific conditions, the blooming step can be completely omitted, but these conditions are relatively demanding, involving both the state of the beans and the brewing parameters.

Under what circumstances can pour-over coffee skip blooming?

As mentioned earlier, the role of blooming is to release carbon dioxide that hinders extraction. So when there is no longer any carbon dioxide in the coffee beans interfering with extraction, there is naturally no need to bloom.

But usually we do not wait until the coffee beans have completely degassed before brewing. This is because carbon dioxide does not only have negative effects—its presence also has many positive values. For example, it can allow flavor substances to remain in the beans longer, or slow the rate of water penetration, thereby extending extraction time and improving extraction efficiency.

In addition to using coffee beans that no longer contain carbon dioxide, there is another situation in which blooming can be omitted—namely, adopting brewing methods that themselves do not include a blooming step.

As is well known, there are many kinds of pour-over brewing techniques, and quite a few of them do not include blooming. For example, the drip method, the one-pour method, the stirring method, and so on.

The reason these brewing methods can skip blooming is that they use relatively extreme techniques or parameters to release or bypass the effects of carbon dioxide.

Take the drip method as an example. In the first half, water is added drop by drop, and then it seamlessly transitions into normal pouring for brewing, with no blooming action throughout. But in fact, during the drip-watering stage, the carbon dioxide in the coffee grounds has already basically been released. This is because drip-soaking the coffee grounds takes a relatively long time, and the coffee grounds wetted by water have enough time to complete degassing.

Now let's look at the stirring method and the one-pour method. The stirring method uses forceful manual stirring to quickly bring out the flavor substances and carbon dioxide from the coffee grounds, so long blooming for degassing is naturally unnecessary; the one-pour method relies on high water temperature and fine grinding to improve extraction efficiency and accelerate carbon dioxide release, and likewise requires no dedicated blooming.

There are many similar methods, and Front Street will not list them one by one here. But it is important to understand that these brewing methods place relatively high demands on the barista's understanding. Whether in parameter setting or water-control proficiency, they are more troublesome to execute, so not many people use them in daily practice.

In summary, pour-over coffee can indeed be made without blooming, but the conditions are relatively demanding. Brewing methods that include blooming can help us brew a good pot of coffee simply and consistently, which is also the reason why current mainstream brewing methods all retain the blooming step.

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The above content is compiled by CoffeeHunters, a coffee news website.