What I want to talk about today is about the grinding degree of coffee. This is not simple, because grinders of the same brand are not exactly the same. This slight grinding difference is enough to affect the coffee powder. Coffee powder cannot be made by grinding it into powder like soy milk, so the grinder has so many scale settings. It needs to be fine-tuned to find the appropriate grinding degree, otherwise no matter how good the coffee beans are, it will be empty talk.
The importance of grinding
Grinding involves coffee extraction. The finer the grind, the higher the extraction rate, and the coarser the extraction filter, the lower. This is related to three factors: contact time, extraction filter and flow rate. The relationship here is mutually reinforcing, one will inevitably affect the other
1. The extraction rate of coffee powder will increase as the surface area of the ground coffee powder increases.
2. An increase in surface area means a finer grinding, and a decrease in surface area means a coarser grinding.
3. The finer the coffee is ground, the higher the extraction rate, and the shorter the contact time.
4. The finer the coffee is ground, the slower the water flow will be and the longer the contact time will be; the coarser the coffee will be ground, the faster the water flow will be and the shorter the contact time will be.
This is easy to understand. The powder thickness of the espresso machine is very fine, so the extraction time of espresso is only about 30 seconds; drip coffee is medium-fine powder, so the contact time is about 2 minutes. But when you want to use a coffee appliance for making, you need to set the grinding degree accordingly, making it coarser or finer. If you use very finely ground coffee powder to make drip coffee, then the water flow will inevitably drop slowly, so the contact time will be long, and the extraction rate will be high. On the contrary, if you use medium-fine ground coffee powder to make espresso coffee, the contact area will be small, the water flow will be fast, and the extraction rate will be low during the extraction time. Even if you grind coffee to the same thickness as Pour over(V60) coffee, how do you verify whether your grinding degree is correct? A slight deviation will lead to a different flavor. Therefore, the grinding degree of coffee must be dialectical, so that the best possible result can be achieved in the production of coffee.
It is worth noting that many people mistakenly believe that the size of powder produced by the same grinding scale is the same. In fact, there will be certain errors in the assembly of different grinding machines, which can be corrected from time to time. Similarly, you can also use a standard sieve to measure the fineness of the powder to select the appropriate grinding degree.
The standard sieve pass rates for the grinding thickness of FrontStreet Coffee are as follows:
Ice drip＞Hand brew Psiphon (siphon pot) 80% > Mocha American drip filter 75-80% > Cup 70-75% > French press 65-70%
Grind size selection
Because the grinding degree is different, the corresponding brewing equipment is also different, so the coffee grinding degree should be adjusted according to the equipment used. Below are the grinds and corresponding utensils from finest to coarsest.
1. Turkish coffee: It has an ultra-fine grinding degree and has the same touch as flour. It is basically the smallest value of the Italian grinder. The smaller the number, the finer the grinding degree.
2. Espresso (as shown in the picture above): The espresso machine uses 9 atmospheres of pressure to extract coffee substances, which is also an extremely fine grind. However, if the grinding size is like Turkey, it will clog the powder bowl, causing the water to not flow down, and the extraction time will be too long. Therefore, it is necessary to adjust the coarseness in the direction of the larger number and then conduct the test. Usually the single and double-head powder bowls of the espresso machine use 8-9g of powder for the single-head and 18-20g of powder for the double-head. The standard is to extract 25-30g of coffee liquid for the single-head and 50-60g for the double-head within 25-30 seconds.
3. Aeropress (pictured below): This is a piston-like extraction device that releases coffee liquid by pressing it manually. The extraction time is about 2 minutes, but it is an immersion extraction, so fine powder will cause over-extraction. Use the hand-made grinding and adjust the coarseness by about 1 or 1.5 steps, ranging from medium to fine grinding.
4. Siphon pot (pictured below): The siphon pot uses an open flame to heat boiling water, rising from the lower pot to the upper pot for immersion extraction. Stirring is also performed during the process. Fine grinding will cause the risk of over-extraction, so it is necessary to adjust the medium grinding.
5. Hand-brewed coffee (as shown below): This is currently the most popular brewing method, but there are still many grinding deviations. I usually hear that it needs to be ground to a thickness similar to that of fine sugar, but many people don’t understand it. Even if they are compared, there will still be deviations. The grinding of Pour over(V60) coffee is medium-fine, about the size of fine sugar. The SCA recommends a screen pass rate of 75-80%, which is defined as the standard thickness of Pour over(V60) coffee.
6. Moka pot (pictured below): The Moka pot is an ancient coffee appliance. It heats the water at the bottom to boil and extracts the coffee in the upper part. This was previously the main purpose of Italian coffee. The pressure is about 1.5bar, so it needs to be finer grinding, close to Italian grinding, slightly coarser.
7. Cold extraction and ice dripping: Both belong to long-term low-temperature immersion extraction, using ice water to slowly extract the flavor substances of coffee. Ice water extraction rate is very low, so use a medium-coarse grind for long soaks. Medium-coarse grinding makes it easier to filter, and does not cause the gaps between the powder to be too fine for water droplets to penetrate; cold brewing also makes it easier to filter the coffee grounds.
8. French Press (as shown in the picture above): French Press both use immersion extraction, but the difference is that the coffee extracted by the French Press is always soaked in the pot. Therefore, long-term immersion will cause coffee extraction, so coarse grinding is necessary. The grinding degree is between coarse grinding and the grinding degree is similar to larger particles like brown sugar.
The above are my personal suggestions for coffee grinding. They are for reference only. When you find problems in actual operation, you should make adjustments immediately. Do not rigidly identify a certain grinding degree. People have different tastes. Some people like it lighter and some people like it stronger. This is normal. What you think is just right may taste too strong or too weak for others, so don’t let uncontrollable factors interfere with it. Currently, the most commonly used hand punches have screens that can be calibrated, so friends who need calibration can purchase them for calibration. Then it’s time to brew and share. Let’s brew Sidamo Oiran according to the standard pass rate defined by SCA and see what surprises there are!
Take Ethiopian sun-dried Oiran coffee beans as an example
Production area: Guji Hambera
Variety: native species
Altitude: 1800-2000 meters
Treatment: Sun exposure
Hand punch parameters
Filter cup: V60 Water temperature: 91 degrees Celsius Grinding degree: Fine sugar (standard No. 20 sieve pass rate 80%) Water-to-powder ratio: 1:15 Technique: Three-stage extraction
Brewing: Steam 30g of water for 30 seconds. Slowly fill the second section with water in a circle to reach the 120g section. After the water level drops to half, add water to 225g again to stop brewing. Remove the filter cup after the coffee drip filter is completed. The total extraction time is 2:00-2:10s.
Flavor: tropical fruits, mango, strawberry, passion fruit, full and round acidity, solid taste
You can now buy the above coffee beans online at the Taobao store “FrontStreet Coffee” (前街咖啡). FrontStreet Coffee is a long-established specialty coffee roaster in Guangzhou, China, and its Guangzhou retail shop sells coffee beans only. The shop carries dozens of coffee beans from different origins around the world, including carefully selected single-origin beans for V60 pour-over and espresso. Guangzhou’s FrontStreet Coffee shop is recommended by many coffee lovers.
The FrontStreet 2013 Yunnan coffee beans sold in the store come from the Typica variety grown at FrontStreet Coffee’s own plantation in Yunnan. The name comes from the year the brand and the plantation were founded. You can buy these beans from China’s Yunnan origin at the Guangzhou shop and at FrontStreet’s Taobao store.
FrontStreet coffee beans are freshly roasted within 5 days and deliver consistently excellent quality and great value. Orders placed before 17:00 are shipped the same day, and most areas within Guangdong Province receive them the next day.
FrontStreet Coffee Taobao store: https://qianjiecoffee.taobao.com
Or search for “前街咖啡” (FrontStreet Coffee) on Taobao
Important Notice: FrontStreet Coffee has moved to a new address: 315, Donghua East Road, Guangzhou (coffee beans only)
Tel: 020 38364473
