Can everything be concentrated? Is it good to extract different ingredients together with coffee? What is the channel effect of coffee?

If we want to add some extra aroma or flavor to coffee, it is a very common practice to add other ingredients to the coffee to let the coffee gain their aroma/flavor. For example, if we want coffee to have a certain fragrance, we can soak some kind of dried flowers in the coffee; if we want to add some sweetness to the coffee, we will add sugar or syrup to the coffee...

However, this practice is usually troublesome and time-consuming (relatively speaking). The soaking time and stirring action will add a lot of work to the making of coffee. Therefore, many witty friends will think: If we add ingredients to the coffee extraction process, will we be able to directly bring out the aroma and taste of these ingredients together with the coffee substance by hot water? This not only saves time and trouble, but also makes the taste more complete and natural.

For most coffee making, this practice can effectively reduce the production process. However, only Espresso Front Street does not recommend this! Why? Because the coffee made this way is difficult to drink.

Why not recommend adding something to espresso powder to extract it? In the previous two days of "Coffee made from powder with a difference of 0.5 grams, can you tell the difference?" In this article, Qianjie shared that the average pressure used in coffee machines when extracting and concentrating is about 9bar. This 9bar pressure acts on a 58mm diameter powder cake, which is about 240 kilograms, which is about the weight of three adults. Such high pressure will cause the substances in the coffee powder to be extracted in a short period of time, but it will also make the extraction more difficult to control. If the extraction time is two seconds longer and two seconds shorter, and the amount of coffee powder is more and less, the quality of the extracted matter will be very different.

In addition, such efficient extraction can easily cause water to "walk" aside, making it impossible for coffee to obtain uniform extraction. Because water is well known to be inert, it will flow preferentially where it flows easily. Especially for espresso extraction environments, this phenomenon will be amplified. Because of this, we need to evenly fill the coffee powder. The reason why espresso requires pressure-assisted extraction is that it wants to quickly extract the substances in the coffee in a short period of time to make a cup of coffee. Then, according to Fick's Law, the rate of material release is positively related to the contact area. So we need to expand the contact area of coffee by refining the grinding of coffee beans, thereby increasing the rate of substance release.

The refinement of the grinding degree will reduce the gap between the powder and the powder, and after filling, a dense and water-tight powder cake will be formed. Therefore, pressure is needed to allow hot water to pass through the coffee powder layer, thereby quickly bringing out the coffee substance. But if a piece of "airtight" powder cake suddenly appears with several channels that are easy to flow, then during extraction, hot water will flow into these channels. Eventually, the coffee powder within the channel is over-extracted, while the coffee powder outside the channel is under-extracted. This is the so-called "channel effect." This is a very common phenomenon for espresso that uses pressure-assisted extraction.

Then why does Front Street take such a big turn to introduce the channel effect? Doesn't seem to have much to do with the theme? (Trouble first rule out hydrology) But in fact, the relationship between the two is closely connected! The reason why the powder cake produces channels is nothing more than that the distribution of coffee powder is not uniform enough. Some places have more coffee powder and some places have less coffee powder. Or, some places have high density and some places have low density. There are many reasons for these situations, such as uneven cloth powder, uneven filling, or the addition of foreign objects destroys the structure of the powder cake. Then the content mentioned at the beginning of the front street belongs to the third point!

Whether it is adding chopped flowers, sugar, salt and other condiments to the coffee powder, no matter how uniform the cloth powder is and how smooth the pressure is, the structure of the powder cake will be destroyed due to the presence and dissolution of these materials during the extraction process, and then a channel will be created. Qianjie had done relevant experiments last year. Add 5 g of granulated sugar to the powder cake and extract it. As a result, concentration not only frequently sputter during the extraction process, but also the taste of the coffee is indescribable due to the uneven extraction. These are all the consequences of the generation of channels. The most important thing is that sugar and coffee did not blend well in the end, and the feeling of surprise when drinking was very strong.

Not only that, if you put in some ingredients with grease or other difficult to clean, such as butter, congratulations, there may be a lot to do after the production is completed. Last year, it was very popular to put a piece of butter on the bottom of a powder bowl to make the "Butter Coffee Rash Waterfall." A friend on Qianjie not only failed to drink the delicious butter coffee after trying it, but also spent a long time cleaning the coffee machine. It can be said that it is a huge gain.

To sum up, you can see why it is best not to add other ingredients to the extraction of espresso coffee. Because doing so will not allow the material to blend perfectly with the coffee, it will also interrupt the uniform extraction of the coffee and make the coffee difficult to drink, and it will also easily add a lot of extra work. Therefore, if you want to add other flavors to your espresso, it is best to mix them extra after the coffee extraction is completed, so that there will not be too many unstable factors ~

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