Front Street shared in the article "The Importance of Cloth and Pressed Powder" that in the preparation process before espresso extraction, whether the coffee powder is evenly distributed in the powder bowl and whether the force is applied evenly during filling will affect the extraction and affect the taste of espresso. But because there is no mention of the force you should use to press the powder, many friends sent private messages to Front Street in the background: How hard should you use to press the powder?
In fact, Front Street has shared several test articles on the strength of pressed powder before, but because the articles only contain experimental comparisons, I believe many friends cannot understand them thoroughly. Therefore, today Front Street will focus on sharing: the impact of the strength of the pressed powder on extraction, and what is the concept of the 9bar pressure of the coffee machine. Why mention the pressure of the coffee machine? Just look below to find out!
Extraction experiment
Well, first of all, in order to make the extraction effect better, we give priority to using medium-dark roasted fresh Italian beans: the first one is the Front Street classic blend, which uses a combination of Brazilian, Mandheling and a small amount of Robusta. It has a rich caramel aroma, buttery smoothness, long-lasting aftertaste, and delicate oil. It is very suitable for novices and home coffee machines.
The second one is the basic blend of Front Street black cocoa. It is positioned as delicious, inexpensive and cost-effective. Therefore, the flavor is nutty, chocolatey and slightly acidic, with a balanced taste and moderate oil. It is suitable for matching with various fancy coffees. The key is that it is affordable. It is not only affordable for daily life at home, but also the first choice for many managers to open a store.
Let’s get straight to the point. First, let’s take a look at the changes in the extraction time and the taste of espresso under different filling pressures with the same amount of powder. The amount of powder used is 20g, the target liquid weight for extraction is 40ml, and the filling pressure is 2kg for light filling (that is, pressing lightly), and 18kg for heavy filling (that is, pressing hard). In order to ensure the stability of the results, Front Street extracted a total of 6 concentrated portions, and then took the average extraction time. The results obtained are as follows:
The average time for three portions of lightly packed powder with 2kg is: 33 seconds.
The average time for three portions of pressed powder with a weight of 18kg was: 34 seconds.
In terms of taste performance, there is almost no big difference between the two: a balance of sour, sweet and bitter, with outstanding flavor. But things didn’t end here. Front Street then extracted two special concentrates. What’s so special about it?
The special thing is that these two concentrates are not filled and pressed after the powder is distributed, but are extracted directly. The extraction results are the same, and the usage time is 33 seconds (as for the taste... I will tell you later). We can see from the extraction time that the extraction time does not change significantly whether it is light filling, heavy filling, or no pressure filling.
This may be somewhat different from the understanding of most friends. Front Street once believed that when the force of the pressed powder we use is greater, the powder can be pressed more tightly, and the extraction time will be relatively prolonged due to the increase in the resistance of the powder cake, thus improving the extraction efficiency. In fact, this is not the case. The reason is simple, because many people ignore the extraction method of coffee machines.
How strong is the extraction pressure of a coffee machine?
As we all know, espresso machines use pressure to quickly make a cup of coffee in a short time. Generally speaking, during the espresso extraction process, the coffee machine will use 9 standard atmospheric pressure for extraction, which is what we often call 9bar (normally it will float between 7 and 12).
Maybe because the number is in single digits, many friends can't understand how big this force is. It doesn't matter. Let's do a simple conversion: 1bar of the coffee machine exerts a force of about 27kg on the powder cake in a 58mm powder bowl. Then 9bar is 27*9=about 243kg, which is equivalent to the weight of 4 adults. One can imagine why the coffee machine can extract the substances in the coffee so quickly.
So we can know that no matter how hard the pressure is filled, it is not worth mentioning in the face of a pressure as high as 9bar. But this raises another question: Why do we need to press powder? If the filling is ineffective, wouldn’t it be better to extract it directly after spreading the powder?
Why press powder?
This problem is actually very simple, because we need to reduce the channel effect. As the saying goes: Water flows downwards, because water is inert, so it will flow where it flows easily. The same goes for the extraction process! Without packing, there will be a lot of gaps between the powders. These gaps will allow hot water to pass through during the extraction process, causing uneven extraction.
The reason why Front Street did not release the flavor experience in the pressure-free extraction above is because the uneven extraction caused a negative expression of the flavor. Therefore, we need to eliminate the gaps as much as possible through appropriate filling and pressure, so that hot water can be extracted more evenly. The force does not need to be too much, just moderate (press the hammer to the bottom).
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
