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The coarseness of the grind directly affects the contact area between coffee and water as well as the extraction time, and it directly impacts the taste of the coffee. But at the same time, coffee grind size is also the biggest headache for many people! In this article, Front Street will explain how to determine what grind size to use for different coffee beans.
First, we need to make sure that the single-origin coffee beans or espresso blend beans we buy are freshly roasted!
When buying single-origin coffee beans or espresso beans, we must buy beans whose packaging has a one-way exhaust valve and a roasting date on it. The "one-way exhaust valve" (the small button-shaped 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 check the roasting date. Because coffee beans produce a large amount of carbon dioxide inside them during the roasting process, 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 coffee beans that have just been roasted, the large amount of carbon dioxide continuously released during brewing will make the entire extraction process very unstable. So how long should they rest? Front Street suggests resting light-to-medium roast coffee beans for 3-4 days, and medium-dark roast 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 beans. In addition to carbon dioxide, the freshness of coffee beans also determines the aromatic substances responsible for coffee's flavor and aroma. These small-molecule aromatic substances volatilize faster than the large-molecule substances that represent coffee's bitterness. Therefore, the less fresh the coffee beans are, the less carbon dioxide and aromatic substances they contain, and the fewer extractable substances there are.Front Street suggests that roasted coffee beans are best consumed within 2 months, and if already ground into powder, best consumed within 20 days. If the coffee beans are no longer fresh, no amount of grinding adjustment will help~
How does coffee grind size affect the flavor of coffee?
1. At the same weight, a finer grind requires more cuts, increasing the surface area, and increasing 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 particle to its center the shorter the time for water to reach the inner part of the coffee particle for extraction / the easier it is to extract coffee flavor substances.
Simply put, under the same other 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 coffee.
What happens when 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 time during brewing is longer. A finer grind results in smaller coffee particles, increased surface area of coffee particles, and more places where water can extract coffee substances, so the concentration and extraction yield increase. The coffee tastes rich, with obvious bitterness and astringency, while other flavors are masked.
What happens when 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 the filtration time during brewing is shorter. A coarser grind results in larger coffee particles, reduced surface area of coffee particles, and fewer places where water can extract coffee substances, so the concentration and extraction yield decrease accordingly. The coffee tastes weak and bland, with a light mouthfeel and almost no flavor.
How do we determine coffee grind size?
Front Street here recommends using a No. 20 sieve (mesh size 0.85mm) to calibrate grind size. Then use 10g of coffee beans, grind them roughly, pour them into the sieve and sift. After fully sifting, check how much coffee powder ends up in the tray below the sieve, and calibrate the grind size based on the pass rate. Front Street Coffee (FrontStreet Coffee) grind size standard sieve pass rates: Cold Drip > Pourover, Syphon 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 with a 0.85mm sieve pass rate of 80-85% for brewing light roast coffee. For medium roast coffee, a grind with a 0.85mm sieve pass rate of 70%-75% is used. For dark roast coffee, a grind with a 0.85mm sieve pass rate of 65%-70% is used. However, everyone's requirements for coffee strength are different. These data are for reference only, and everyone can still adjust to different degrees according to their own taste preferences.
What if you don't want to buy a coffee grind calibration sieve?!
Front Street knows this whole process is quite troublesome, so here Front Street has put together a small guide to coffee grind sizes, so you can see roughly what grind size to use for your coffee brewing tool. Front Street divides coffee grind 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 to create resistance against the high-pressure hot water, so that the essence of the coffee can truly be extracted. The more uniform and delicate the grind, the tighter the tamped coffee puck, 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. The main reason is that the entire drip bag is made of filter paper, and the flow rate is very large. Unlike pourover, which has a narrowed opening, such as the commonly used three-hole dripper, which actually slows down the water flow rate, drip bags need fine grounds to increase the extraction area and extract more substances.
Medium-fine: suitable for brewing light-to-medium roast coffee (various pourover drippers), recommended: Front Street Fruit Ding Ding, Front Street Huakui, Front Street Geisha, Front Street Strawberry Candy
Front Street uses medium-fine grind when brewing light-to-medium roast coffee beans, about the size of fine granulated sugar, with a grind pass rate between 75%-80%. Because light-to-medium roast coffee beans generally have rich acidity, a medium-fine grind can enhance the overall sweet-and-sour expression of the coffee~
Medium: suitable for brewing medium-dark roast coffee (various pourover drippers), recommended: Front Street Jamaica Blue Mountain, Front Street Golden Mandheling, Front Street Huilan
Front Street uses medium grind when brewing medium-dark roast coffee beans, about the size of coarse granulated sugar, with a grind pass rate between 70%-75%. Medium grind is less likely to produce extra fine powder, and is also less likely to cause over-extraction due to unstable water flow control at the beginning, which can lead to a large amount of water pooling in the dripper and soaking the coffee grounds.
Coarse: suitable for making coffee with a French press
The French press extracts the most original taste of coffee through a 4-minute immersion. Compared with pourover coffee, its coffee liquid is relatively cloudy. The reason is that when filtering with a metal mesh, the aperture is relatively large, so in terms of grind size we need to use coarse grounds. First, the coffee flavor is slowly extracted, and second, when the French press presses down the filter mesh, the coffee grounds will not "escape" through the gaps in the mesh and mix with the coffee, affecting the mouthfeel when tasting.
The above content is compiled by CoffeeHunters, a coffee news website.
