What can the coffee bed reveal during coffee extraction?
During pour-over brewing, the dripper shows several readable signals. A large bloom dome and good water retention point to fresh beans with plenty of carbon dioxide and a certain roast level. Whether the bed can be lifted relates to ground density. Foam color tracks the pouring path, and drawdown speed connects to grind size, bed density, and fine particle clogging. A deep crater does not equal better taste.
Blooming releases carbon dioxide, and the bubbles push the coffee bed upward into a dome. More carbon dioxide means a larger dome and slower drainage, so the bed stays moist longer; less gas gives the opposite result. Grind size and coffee particles also shape flow, since fines can block the filter and stall the drawdown. These signs are useful references when adjusting brewing parameters.
When brewing pour-over coffee, there are actually quite a few clues hidden in the dripper. The size of the dome that forms on the coffee bed during blooming and how well it retains water can reflect the freshness of the coffee beans and the roast level; whether the coffee bed can be lifted is closely related to the density of the coffee grounds; the color changes of the foam on the surface can help us track the pouring path; and the speed of drainage is related to grind size, bed density, and fine particle clogging. As for the deep coffee bed crater that many beginners obsess over, it does not directly equate to better taste—it is more just a reflection of the pouring method. In this article, Front Street will break down these readable pieces of information during the brewing process one by one, to help you have a few more bases for judgment when adjusting parameters.
You know what, there really are some pieces of information that can be gleaned from the dripper, and quite a lot of them at that. For example, the freshness of the coffee beans, the density, the grind size, the pouring path and method, and so on and so forth. All of these can be read during the brewing process! So what Front Street wants to share today is which aspects of the brewing process we can read information from, and what kinds of information we can get.
1. The Degree of Doming During Blooming Blooming is a preparatory step included in most brewing methods, because blooming can release a large amount of carbon dioxide from the coffee grounds, allowing the hot water poured in afterward to better dissolve out the flavor compounds. During the blooming process, the released carbon dioxide forms bubbles as it gets wrapped by water, and these bubbles then push the coffee bed upward, forming a dome like a small hill.
The size of the dome on the coffee bed, as well as its water retention, can help us judge the freshness of the coffee, because both states mainly depend on the carbon dioxide content. When the carbon dioxide content is higher, the dome that forms on the coffee bed will be larger, and vice versa; then, because the bubbles create resistance and slow down the drainage speed, when the carbon dioxide content is higher, its water retention effect will be stronger, and the coffee bed can remain moist for a longer time. Conversely, when the carbon dioxide content is insufficient, the coffee bed will quickly dry out and collapse. So we can tell the freshness of a coffee bean from the size of the dome and the degree of water retention during blooming, because the fresher the coffee beans are, the more completely the carbon dioxide stored during roasting is retained, and the larger the dome during blooming will naturally be, and the better the water retention effect will be.
Dark-roasted coffee tends to form a larger dome than light-roasted coffee, because the carbon dioxide content is also tied to the roast level. The darker the roast, the more carbon dioxide accumulates in the coffee beans. At the same time, the expansion rate of the beans will be greater, so the dome that forms will naturally be relatively larger.
2. The Height of the Coffee Bed Lifting the coffee bed is a pouring technique we often use when brewing coffee! Specifically, this technique refers to increasing the pouring flow rate so that the pouring rate exceeds the drainage rate, thereby raising the water level, and then the coffee grounds in the dripper can rise as a whole along with the water level, finally distributing evenly around the dripper. The benefit of this technique is that it allows us to reduce bypass water while allowing the hot water to extract the coffee grounds more evenly. (For a detailed introduction, you can search for related past articles.)
But not all coffee beds can be lifted, because this is related to the mass of the coffee grounds. The lighter the roast or the higher the density of the coffee grounds, the heavier they are and the less able they are to be lifted. So from whether the coffee bed can be lifted, we can judge the approximate density of the beans and then find a corresponding extraction plan. For example, when the coffee bed cannot be lifted, if we do not want too much bypass water to make the brewed coffee weak and tasteless, then we had better appropriately reduce the flow so that the hot water can pass through the coffee bed as much as possible to perform extraction.
3. The Color of the Foam During the coffee brewing process, many bubbles float on the surface of the coffee liquid. They are the bubbles formed by the release of carbon dioxide that Front Street mentioned earlier. The color of these bubbles changes continuously as brewing progresses, from dark brown at the beginning to golden, then to light yellow, and finally to whitish. And it is precisely from the color of these bubbles that we read information during brewing.
This is because the color of these bubbles mainly comes from the coffee grounds; some extremely small and extremely light coffee particles mix into the foam and give it color. During the brewing process, the hot water we pour washes these fine particles away from the foam, and without the fine particles, the color of the foam gradually fades. So, when we see the color of certain foam gradually becoming lighter or even whitish, it means our pouring was concentrated in those areas. In other words, from the color of the foam, we can see the pouring path.
4. The Drainage Speed Next is the drainage speed. The drainage speed is affected by many factors, such as density, grind, dripper, and various other factors. But under normal circumstances, the drainage speed mainly depends on the grind size and the density of the coffee beans. When the drainage speed is faster, it usually means the coffee grounds are coarser, the hot water has more room to flow, and the drainage speed is therefore faster; when the drainage speed is slower, it means the grind is finer or the density of the coffee grounds is higher, the gaps between the coffee grounds after they settle are smaller, there is not much room for the water to flow, and the speed therefore decreases.
Another reason for slow drainage is too many fine particles, which clog the filter holes and slow the drainage speed. But because there are too many factors affecting drainage speed, this situation usually requires combining the fifth point to reach a conclusion. But what everyone needs to know is that we cannot directly tell whether a cup of coffee tastes good or not from the speed of drainage. Because besides extraction time, many other factors affect coffee extraction~ So in the end we still have to combine it with taste before deciding whether parameters need to be adjusted.
5. The Shape of the Coffee Bed Crater Last is the shape of the coffee bed crater! Many friends, when they first get started, pursue a deep and even coffee bed crater after brewing ends, both because such a deep crater is even and symmetrical and looks pleasing, and because it is often said online that the appearance of this kind of deep crater means the coffee will taste good.
But in reality, the formation of the coffee bed crater has no direct relationship with whether the coffee tastes good; it merely reflects our pouring method during brewing. For example, the technique of lifting the coffee bed can promote the formation of a deep crater. And besides that, there are also many different types of coffee bed craters, because, as Front Street said, they reflect different pouring methods. For example, the appearance of a flat-bottomed crater indicates that we did not use too strong a flow during pouring; a断层crater means our flow was too strong, or too concentrated at a certain edge... Because there are too many types of coffee bed craters, Front Street will not expand on them here. Interested friends can go to this article to learn more, "The Complete Guide to Pour-Over Coffee Bed Craters"~
So the above is all the content of this article. If there are any other details worth paying attention to during the brewing process, everyone is welcome to leave a comment in the comment section and exchange ideas~ - END -
The above content is compiled by CoffeeHunters, a coffee news website.
