The grind size of coffee directly affects the contact area between coffee and water as well as the extraction time, and it will directly influence the taste of the coffee. But at the same time, coffee grind size is also the most headache-inducing thing for many people! In this article, Front Street will talk about how to determine what the grind size should be for different coffee beans.
First, we need to make sure that the single-origin coffee beans or espresso blend coffee beans we buy are freshly roasted!
When buying single-origin coffee beans or espresso beans, we must buy coffee beans whose packaging has a one-way exhaust valve and the coffee bean roasting date. The "one-way exhaust valve" (the button-shaped small hole at the top of the coffee bag) is designed to allow coffee beans to release naturally produced carbon dioxide while blocking other outside gases from entering the packaging. Every bag of coffee beans from Front Street Coffee (FrontStreet Coffee) is freshly roasted and uses packaging with a one-way exhaust valve.
After buying coffee beans, we can look at the roasting date, because during the roasting process coffee beans produce a large amount of carbon dioxide inside the beans, so we need to give the beans 3-7 days to release carbon dioxide on their own, commonly known as resting the beans. If we directly brew freshly roasted coffee beans, a large amount of carbon dioxide will continuously be released during the brewing process, making the entire extraction process very unstable. So how long should they rest? Front Street recommends resting light-medium roasted coffee beans for 3-4 days, and medium-dark roasted coffee beans for 4-5 days.
As just mentioned, the most direct manifestation of coffee bean freshness is the release of carbon dioxide from the coffee beans. In addition to carbon dioxide, the degree of freshness of coffee beans determines the aromatic substances responsible for coffee flavor and aroma. These small-molecule aromatic substances volatilize faster than the large-molecule substances that express coffee bitterness, so the less fresh the coffee beans are, the less carbon dioxide and aromatic substances they have, and therefore the fewer extractable substances there are. If the coffee beans are already stale, no amount of grinding will help~
How does coffee grind size affect the flavor of coffee?
1. At the same gram weight, the finer the grind, the more times it needs to be cut, the larger the surface area, and the greater the area where water can contact the coffee grounds.
2. The finer the grind, the finer the particles the coffee grounds are cut into the shorter the distance from the surface of the coffee grounds particles to their center the shorter the time for water to reach the inner part of the coffee grounds particles for extraction / the easier it is to extract the flavor substances of the coffee.
Simply put, under otherwise identical parameters, the finer the particles, the higher the extraction yield; the finer the coffee is ground, the larger the contact area with water, and the higher the concentration of dissolved coffee; conversely, the coarser the coffee is ground, the smaller the contact surface area with water, and the lower the extracted concentration of the coffee.
What happens if the coffee is ground too fine?
From the appearance of the particles, the particle size is smaller, and because the particles are smaller, the spacing between particles is shorter, making it harder for water to pass through, so the drip filtration time during brewing is longer. A finer grind results in smaller coffee grounds particles and an increased surface area of the coffee particles, so the places where water can extract coffee substances increase, thus increasing concentration and extraction yield; the coffee tastes rich, with obvious bitterness and astringency, while the other flavors are masked.
What happens if the coffee is ground too coarse?
From the appearance of the particles, the particle size is larger, and because the particles are larger, the spacing between particles is greater, making it easier for water to pass through the coffee grounds, so during brewing, the filtration time is shorter. A coarser grind results in larger coffee grounds particles and a reduced surface area of the coffee particles, so the places where water can extract coffee substances decrease, and therefore concentration and extraction yield also decrease; the coffee tastes weak and bland, with a light body and almost no flavor.
How do we determine coffee grind size?
Front Street here recommends everyone use a coffee bean grind size cupping calibration sieve No. 20 (mesh size 0.85mm). Then use 10g of coffee beans for a rough grind and pour them into the sieve to sift. After completely sifting, see how much coffee powder finally falls into the tray under the sieve, and calibrate the grind size through the passing rate. Front Street Coffee (FrontStreet Coffee) grind size standard sieve passing rate: cold drip > pour-over siphon 80% > moka pot American drip 75-80% > cupping 70-75% > French press 65-70%.
Of course, for coffee beans of different roast levels, the corresponding grind size used is also different. For example, Front Street uses a grind size with a passing rate of 80-85%% through a 0.85mm aperture sieve when brewing light roast coffee. For medium roast coffee, a grind size with a passing rate of 70%-75% through a 0.85mm aperture sieve is used. For dark roast coffee, a grind size with a passing rate of 65%-70% through a 0.85mm aperture sieve is used. However, everyone's requirements for coffee strength are different, so these data are for reference only, and everyone can still adjust to different degrees according to their own taste preference for strength.
What if you don't want to buy a coffee grind size calibration sieve?!
Front Street knows that this whole process is quite troublesome, so here Front Street has made a small summary of coffee grounds grind sizes, so you can see roughly which grind sizes to use with your own coffee brewing tools. Front Street divides coffee grounds coarseness into 5 types: extra fine, fine, medium-fine, medium, and coarse.
(From left to right: coarse, fine, extra fine)
Extra fine: suitable for making espresso (moka pot, espresso machine)
When making espresso, you must tamp the coffee grounds firmly so that they create resistance to the high-pressure hot water, and only then can the essence of the coffee truly be extracted. The more uniform and delicate the grind, the tighter the coffee grounds after tamping, and the more balanced the resistance to water. The espresso "squeezed" out this way will have rich crema.
Fine: suitable for making drip bag coffee
This grind size is Front Street's "soul mate" for making drip bag coffee. This is mainly because the entire drip bag is filter paper, so the water flow is very large. Unlike pour-over, which has a narrowed outlet, such as the commonly used three-hole filter cup, which actually slows down the speed of water flowing out, drip bags need fine grounds even more to increase the extraction area and extract more substances.
Medium-fine: suitable for brewing light-medium roasted coffee (various pour-over coffee filter cups)
When brewing light-medium roasted coffee beans, Front Street uses medium-fine grounds, about the size of fine granulated sugar, with a grind size between 75%-80% passing rate. Because light-medium roasted coffee beans generally have rich acidity, a medium-fine grind size can enhance the overall sweet-and-sour expression of the coffee~
Medium: suitable for brewing medium-dark roasted coffee (various pour-over coffee filter cups)
When brewing medium-dark roasted coffee beans, Front Street uses medium grounds, about the size of coarse granulated sugar, with a grind size between 70%-75% passing rate. Medium grounds are not prone to producing extra fine powder, and are also less likely to cause a large amount of water to accumulate on the filter cup and soak the coffee grounds due to unstable water flow control at the beginning, thereby over-extracting the coffee.
Coarse: suitable for making coffee with a French press
The French press extracts the most original taste of coffee by steeping for 4 minutes. Compared with pour-over coffee, its coffee liquid is relatively cloudy because the metal filter has a larger aperture during filtration, so in terms of grind size we need to use coarse grounds. First, the flavor of the coffee is slowly extracted, and second, when the French press presses down the filter, the coffee grounds will not "escape" through the gaps in the filter and mix into the coffee, affecting the mouthfeel when tasting.
The above content is compiled by CoffeeHunters, a coffee news website.
