Steaming, or "blooming," is a step in coffee extraction that is often mentioned but easily misunderstood. This article begins with the pre-infusion design of segmented-water coffee machines, explaining the principle by which blooming enhances extraction and locks in aroma, while also pointing out that manually imitating blooming on household machines without a segmented function will instead cause a loss of the essence. The article further introduces blooming methods for different devices such as pour-over, American drip, Belgian Royal siphon, and siphon pots, and, drawing on experience providing catering to coffee shops, explains the changes in coffee aroma and smoothness after blooming, for the reference of coffee enthusiasts.

The so-called "steaming" refers to covering the coffee grounds during certain stages of coffee preparation, which is commonly called "blooming." My first encounter with this concept came from coffee machines with a segmented water-supply structure, that is, machines with a pre-infusion function. They first deliver a small amount of water to the coffee puck while keeping the pressure from being released, allowing this water to pre-activate the coffee's flavors and perform blooming. This extraction method has many advantages, and I think the most important one is that it allows the essence of the coffee to be extracted more completely and keeps as much of the coffee's aroma in the cup as possible. But there is an easy pitfall here: if the coffee machine itself does not have a segmented water-supply design, yet you insist on manually dividing extraction into two stages, not only will the blooming effect not be achieved, but you will also lose more than you gain. The reason is that the first portion of water injected does indeed come into contact with the coffee grounds, but once the button to stop extraction is pressed, the water used for blooming as well as the coffee liquid extracted earlier will be sent directly into the drain by the machine's pressure-release return system. This kind of operation cannot be called improved extraction; instead, it causes the coffee to lose part of its essence.

Pour-over coffee also follows the idea of blooming. Before the official pouring, first make a hole in the center of the coffee grounds, then pour in a very small amount of hot water, using the coffee grounds' water absorption and expansion to form a "lid" structure, performing the first blooming of the coffee bed. After this "lid" collapses, pour water a second time to form a slightly larger "lid" for a second round of blooming. Only after the two rounds of blooming are completed does the stage of大量 pouring for extraction begin. On the surface, this method does not seem complicated, but in practice it places quite high demands on the operator's technique and experience.

American drip coffee machines have also incorporated blooming into the process. The first two methods complete blooming before extraction ends, while the American drip machine continues blooming after coffee extraction is finished by keeping the coffee on the warming plate. Although the order in which blooming occurs is different, the effects achieved have something in common.

Looking back some years ago, when I was doing opening banquets for quite a few coffee shops, in order to meet customers' concentrated demand for coffee, I often used a siphon pot to first extract a large amount of coffee liquid, store it in a thermos, and then pour it out when guests needed it. This could effectively avoid the awkwardness of coffee supply not keeping up. Originally just an emergency measure, it unexpectedly gave me coffee that had undergone blooming, with an especially rich aroma and a very smooth mouthfeel, with almost no astringency detectable.

My exploration of coffee blooming has only just begun. At present I have only roughly experienced the process and results of blooming. As for the chemical and physical reactions behind blooming, as well as the new aroma arrangements and flavor combinations produced by blooming, they remain unsolved mysteries to me. I am afraid that even if I spent my whole life on it, I would still find it hard to fully understand the answer to this puzzle. Perhaps it is precisely because the mystery of coffee is so difficult to solve that we coffee gourmets never tire of it and flock to it.

………………………………Blooming in the Belgian Royal Coffee Maker………………………………

(Image caption: Belgian Royal Coffee Maker grounds cup)

(Image caption: Before extraction, first pour water into the Belgian Royal Coffee Maker grounds cup for blooming)

(Image caption: Blooming in the Belgian Royal Coffee Maker grounds cup)

………………………………Blooming in the Siphon Coffee Maker………………………………

(Image caption: Add grounds to the upper chamber of the siphon pot first, cover with the lid, and wait for the water in the lower chamber to rise to the upper chamber)

(Image caption: The water that has just risen into the upper chamber of the siphon pot blooms the coffee)

(Image caption: All the water from the lower chamber of the siphon pot has risen to the upper chamber)

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