A big difficulty in making espresso is that we need to constantly adjust the amount of powder, grinding thickness, ratio and other parameters to improve the quality of the coffee so that it can achieve an ideal extraction process within tens of seconds. In addition to observing the flow rate, pressure and extraction time, the way to judge whether it is good or not is that the extracted coffee powder can also provide us with useful information.
Let’s first take a look at what an ideal powder cake looks like:
Just like the ground pit of Pour over(V60) coffee, the even and round bowl-shaped structure means that the water injection method is passed and the grinding is not disturbed. For espresso coffee, because pressure-assisted hot water extraction is used, a large amount of soluble substances can be brought out in a short time with a very small amount of water. At this time, observing the extracted powder cake becomes one of the visual criteria for judging whether there is a problem with the espresso coffee.
Normally, after the extraction, the best state of the powder cake is that it is relatively dry first, with a smooth surface, no water accumulation and obvious holes. When knocked out, it will be a complete block with even color distribution, consistent thickness and not easy to break. But if your pressed powder is difficult to form and your coffee never tastes good, Front Street suggests combining the two to identify the problem.
1. The surface of the powder cake is bumpy.
It can be said that both experienced baristas and newcomers who are just starting to play with baristas have encountered this situation more or less. The bumps on the surface of the powder indicate that the hot water did not get enough room to move during extraction. One of the reasons is that the powder is too thick.
Normally, the lighter the roasted coffee beans, the smaller the volume expansion, and the deeper the roasting, the larger the volume. Therefore, under the same weight, the powder cake of dark roasted beans will be thicker. After absorbing the expansion, the coffee particles will be too close to the water separation network, causing the coffee particles to adhere to it. When the handle is removed, an uneven surface will be seen. At this time, the coffee is often accompanied by insufficient extraction, and the taste is light or sour.
Solution: Make the powder layer thinner by finer grinding + powder reduction.
2. The powder cake has holes.
Perforation is a significant feature of the channel effect, because water is inert. Once the density of the powder cake is unevenly distributed, it will drill through loose areas. At this time, the extraction efficiency is higher where the hot water flows, while other areas will not be extracted enough, and sometimes splashing and flow rate jumps will occur.
Solution: Pay attention to the powder (break up the clumped coffee)
3. Serious water accumulation in powder cake
Contrary to the first situation, this water accumulation problem is mostly caused by the powder layer being too thin. The problem usually lies in the grinding degree. Even for the same coffee beans, when the grinding degree is adjusted to be finer, the gaps between the particles become smaller and the density is higher, so the height of the powder layer will decrease. If the same powder bowl is used, a larger space will be formed between the thinner powder cake and the water separation network, and the hot water will stay on it for a longer time, and serious water accumulation will appear on the surface of the coffee grounds.
Another situation is caused by the coffee machine, that is, the atmospheric pressure of 9 bar, because we need to meet at least two conditions to obtain espresso rich in coffee oil. One is fresh medium-dark roasted coffee beans. For example, Front Street Boutique Blend, Front Street Commercial Blend, and Front Street Classic Blend are all Italian formulas that help us easily extract qualified espresso at home.
And the second key point ishardware equipment, many home users’ coffee machines almost belong to the category of “toy machines”. It is difficult to reach 9 atmospheres of pressure when running, and even emitsClickIf there is a rattling sound and insufficient penetration, it will naturally be difficult to achieve deep extraction. In addition to the water stopping on the powder cake, the coffee liquid may also flow down.
Solution: Adjust coarse grinding + add powder
4. After extraction, the powder cake will be loose, moist and soft.
Compared with the ideal powder cake mentioned at the beginning of the street, the loose or wet and soft state indicates that the hot water has impacted the extraction of the coffee, and each particle becomes sticky due to being saturated with water. The flow rate in this case is generally within the normal range (powder to liquid ratio 1:2, time 25~35 seconds), but it will taste more bitter. The main reason behind this is that there is too little coffee powder. If you also have this kind of problem, you can try adding 0.5~1g coffee powder.
In addition, if you use a double-portion powder bowl to make a single shot with half the amount of powder, it is easy to have this kind of problem. It is recommended to replace it with a single-portion powder bowl.
Solution: Add flour/replace the single-serve flour bowl
5. Keep the powder cake dry and wet at the same time
This situation is very simple. It means that the center of gravity of the pressure is not grasped when pressing the powder, causing the powder cake to be uneven. Front Street usually presses one side of the powder hammer with his thumb and index finger, and then uses the remaining three fingers to wrap the handle of the hammer with the palm of his hand. With his arms vertical, he presses down hard.
6. The bottom of the coffee powder cake is black
During the espresso extraction process, hot water penetrates from top to bottom, reaching the surface of the cake first, and finally the bottom. A uniformly extracted "good cake" usually has a consistent color from the inside to the outside. However, if you remove the handle in advance, the flavor substances in the lower layer may not be released before the extraction is forced to end. In this way, the bottom will be in a dark, semi-moist state, and the coffee will taste thinner because of the missing tail section.
Solution: First extract according to the powder-to-liquid ratio of 1:2. If the extraction time is too long, adjust the coarse grinding degree.
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
