What causes espresso oil to clump? Why does the espresso powder not take shape?

Hello everyone, what Qianjie wants to share today is a summary of those very easy problems in the extraction process of espresso coffee-version 2.0.

It has been more than half a year since the tweet "Frequently Asked Questions on Extracting Espresso Coffee" 1.0 "was shared. As for why the second article was only shared after such a long time, it must be for a reason, and definitely not because Qianjie forgot it. So the question in this collection is still the content shared by Qianjie in a separate post, so Qianjie here still just makes a simple answer, and then a corresponding tweet link will be attached to the title, and friends troubled by the question will click on the link. Learn more about it~So let's not say much and start our sharing today!

FAQ 6: After the extraction, why does water accumulate in the powder bowl? Is the powder cake wet and loose without forming? After we extracted the espresso, the powder cake we saw when we took off the handle was usually relatively dry and did not have as much moisture. But occasionally, we would find a large amount of stagnant water in the powder bowl with the handle that we removed. The powder cake was wet and loose and unshaped.

A situation like this is mainly caused by the amount of powder used! When the amount of powder we use is much less than the recommended amount of powder in the powder bowl, there will be a wide gap between the powder cake and the brewing head, which requires more hot water to fill before extraction can begin. This led to the fact that the pressure relief suction at the end of the extraction could not expel all the hot water in the powder bowl, which in turn resulted in a large amount of water in the powder bowl and the powder cake being loose and unshaped when knocked out. Another situation that can easily occur is that the coffee powder is ground too finely. If the coffee powder is too thin, water will pass through the powder layer slowly because of the high resistance of the powder cake. At the end of the extraction, the powder cake may be drained due to the fact that part of the water failed to pass through the powder layer in time, resulting in a large water content and a wet and muddy shape.

FAQ 7: Why is the powder cake incomplete and not shaped after extraction? Many friends will be curious about how to judge the extraction situation from the state of the powder cake. This has actually been shared in this article before. The specific method is very simple. We only need to observe whether the pressed powder cake is complete and shaped after the extraction is over.

If there are many small holes on the surface of the powder cake, the knocked powder cake is very scattered and unshaped, and the coffee powder in different positions has a large color difference, then Mu Yong doubts that the extraction must not be so uniform! Why? Because these are all phenomena that will occur after the channel effect occurs during the extraction process. ("What channel effect?")

The small holes are actually channels, which are formed because all hot water is concentrated in these places and seeps out; while the powder cake is not shaped because the hot water during extraction does not penetrate evenly, and some coffee powder inside is not fully soaked by hot water. They (Coffee powder moistened by each cup of hot water) cannot be connected with other coffee powders, so the powder cake cracks when knocked out; the same is true for the large color difference. Although the extraction of coffee is not completely uniform, coffee powder in different positions will have a certain color difference, but it will not be too large. When the extraction is uneven, the color difference will be widened, resulting in a greater color difference between coffee powder and coffee powder.

FAQ 8: Why is the fat in espresso coffee agglomerated? Many friends often encounter the problem of grease agglomeration! That is to say, although espresso coffee has very rich oil after extraction, the oil begins to agglomerate and harden after a while, and the liquidity is very low, which greatly affects the production of coffee flowers. The main reason for this situation is that the coffee beans are too fresh.

As we all know, coffee beans that are too fresh will contain very rich carbon dioxide, which will make the extracted espresso rich in fat. Although these oils are rich, they are very rough! Because the oil is composed of countless small bubbles filled with carbon dioxide, and the composition of these bubbles is not only carbon dioxide, but also the lipids of coffee beans. Since the amount of coffee lipids is fixed, when the amount of carbon dioxide increases, although more bubbles will be filled, less lipid will be wrapped around each bubble. This will cause the bubbles to break very quickly, and then the oil will harden because most of the bubbles break, which is called agglomeration, and then affects the production of flowers.

The solution is very simple. We just need to leave it for a while to lose part of the carbon dioxide before extracting it. The oil obtained is a type that is delicate and not easy to agglomerate! At the same time, the taste of coffee will be richer due to the reduction of carbon dioxide, which can be said to kill two birds with one stone~

FAQ 9: Is it too much to have "tiger stripes" in espresso coffee? Sometimes, the espresso grease we extract will have obvious black stripes from time to time, like tiger spots. Many people call this "skin" a symbol of over-extraction, because it is often a feature that occurs only after a long period of extraction.

The fact is that "tiger spot" is not a feature that appears only when it is over-extracted, because it is not burnt coffee grease, but coffee powder that is originally in the powder bowl. The powder bowl of the espresso machine is actually a filtering tool, but it does not have the strong filtering performance of the filter paper, so some substances other than coffee can also be "squeezed" by the coffee machine through the filter holes of the powder bowl, such as coffee grease, and coffee powder! The black stripes on the surface of the grease are the coffee powder that is pressed out of the powder bowl and then floats on the surface of the grease because the particles are smaller and lighter.

Generally, the espresso we extract will not have obvious stripes, that is, there will not be many fine coffee powder. There are two main reasons why tiger spots appear: one is that they are too fine! When the coffee powder is ground too fine, there will be more fine powder. In addition, this will make the powder cake more resistant and the extraction time will be longer, so it will be easier for a lot of fine powder to be pressed out of the powder bowl; another situation is because we shake too much when spreading the powder, so the very fine particles are shaken to the bottom of the powder bowl, which can be easily pressed out during extraction. The existence of fine powder has advantages and disadvantages. The advantage is that it can give coffee a higher mellow feeling and a stronger taste; the disadvantage is that it increases the concentration of bitterness. When there is too much fine powder, the bitterness will be more obvious. Therefore, when you drink it, it will feel like it is too rich.

So, the above are all the common questions about this concentration and extraction. If you have any other questions, please leave a message in the comment area, and Qianjie will open a special topic to share it next time~

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