If you pay careful attention, you will find that there are many different brewing methods in coffee shops, but based on the grinding degree of the coffee powder, it is usually divided into two types. One is grinding as finely as granulated sugar, which is suitable for hand-brew coffee, French press coffee, siphon coffee, cold brew coffee, etc. The other is tiny particles between flour and sand, which is the grinding scale for making espresso.
How to determine the grind size for espresso
According to the definition of Espresso (Italian espresso) by the Italian Coffee Association and WBC, a qualified espresso refers to 1 ounce (about 30ml) of espresso with golden oil extracted from hot water at 90.5~96°C under 9 atmospheric pressure within 20~30 seconds.
Although the above statement does not clearly state the specific thickness of the grinding degree. But as long as we clarify the relationship between time and grinding degree, it will be easy to determine the grinding degree.
As long as there are no problems with human factors such as cloth powder and pressed powder, the finer the coffee grinding particles, the longer the extraction time will be, and the taste will be burnt and bitter, which can easily lead to over-extraction. On the contrary, the coarser the grinding particles will be, the extraction time will be short, and the taste will be sour, which will easily lead to under-extraction.
Therefore, when Front Street faces an unfamiliar Italian coffee bean or replaces a new grinder, the idea of determining the grinding degree is: first determine the extraction plan. Front Street’s default Italian extraction plan is 20 grams of coffee powder (depending on the capacity of the powder bowl), and uses a 1:2 extraction powder-to-liquid ratio (previously) The roasting degree of the sunflower warm sun blend used by the street is slightly lighter than that of ordinary Italian coffee beans, so the ratio of 1:2 is used to highlight the flavor characteristics of sherry coffee and red cherry coffee), that is, 40g of coffee liquid (the weight unit is used because it is more accurate than the volume unit, and the weight of coffee oil is smaller than the volume).
Fixed parameters are used for pressure and water temperature. The pressure of the coffee machine used in Front Street is set at 9bar and the water temperature is 93°C. Then we only need to adjust the grinding degree to achieve the preset time point. Some grinders are equipped with a powder bin, so after each grinding adjustment, the remaining powder needs to be cleaned to avoid affecting the accuracy of the adjustment.
When debugging to within our preset time interval, don’t get too excited. Because what you want is a cup of delicious espresso, you need to taste it to determine whether there are any defective flavors such as bitterness, sourness, wateriness, etc., and secondly, determine whether it has the flavor represented by this coffee. If not, you need to continue adjusting, and at this time the adjustment is not limited to the grinding degree. Because the brewing parameters we preset are based on existing cognitive concepts, and when facing coffee beans that are always unfamiliar to us, we need to consider whether the preset extraction parameters are reasonable.
For example, when testing the Front Street Colombian Hija SOE coffee, if the appropriate parameters (grinding degree, flow rate) are selected, the coffee will have a very rich grape, passion fruit, and citrus flavor. However, if the grinding degree is adjusted to the appropriate grinding degree, the extraction parameters are 20g coffee powder to extract 40g coffee liquid, which takes 30 seconds. When tasting the flavor, you will feel a bit of burnt bitterness. You can reduce the powder by 0.2 to 0.5g to speed up the flow rate, thereby improving the performance of the good flavor.
Therefore, when we judge whether the grinding degree of espresso is correct, we first determine whether the extraction parameters are within a reasonable range, and then taste and test whether the taste is as expected. If not, fine-tuning is required.
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
