Is coffee pre-soak function necessary? What is Italian concentrated pre-soak extraction? How to operate pre-soaking?

Usually, when we extract espresso, we use the default pressure 9bar of the coffee machine for non-stop one-time extraction. However, with the pursuit and research of coffee, a new way of Italian coffee extraction has emerged in recent years, that is, "pre-soaking".

The so-called pre-soaking is to use a small amount of hot water to wet the powder layer in advance, or to control the pressure to the lowest level, so that the coffee powder in the powder bowl has a soaking time. When the soaking is finished, the coffee machine begins to apply more pressure and water to dissolve the flavor substances in the coffee. The purpose of pre-soaking is simple: to wet the coffee beans and exhaust them. Therefore, pre-soaking is often compared to the steaming of hand-brewed coffee. But many friends feel puzzled, their usual extraction of espresso is already very good, what is the use of pre-soaking?

Under the extraction pressure as high as 9bar, the extraction of espresso can indeed ignore the effect of a large amount of carbon dioxide on the extraction and bring out flavor substances. But the existence is reasonable, and the existence of pre-immersion just means that there is demand. In some cases, the use of pre-soaking does help to improve the quality of coffee. But to know when to use pre-soaking, we need to know about pre-soaking.

The purpose of pre-soaking has two purposes, one is to improve the extraction rate, and the other is to reduce the phenomenon of uneven extraction. As we all know, one of the most common negative phenomena in the extraction process of espresso is the channel effect. Because dried coffee powder is hydrophobic, this property makes it easier for inert water to flow to places where it is easier to flow.

If pressed powder can be evenly filled and pressed, it will not have much impact. But if the filling pressure of pressed powder is not uniform enough, it will lead to some low-density channels in the supposedly airtight pressed powder, and then under the action of pressure and inertia, hot water will concentrate to flow to these places. And then form the channel effect. The coffee powder in the channel range is over-extracted, while the coffee powder outside the channel is unevenly extracted. (the holes in pressed powder below are all channels)

Through pre-soaking, pressed powder can be fully moistened and expanded before a large number of "water armies" arrive, reducing hydrophobicity, thereby reducing the channel effect. At the same time, as the coffee powder is infiltrated and carbon dioxide is released in advance, the following hot water will have a more efficient extraction and a faster flow rate (the presence of carbon dioxide slows down the flow rate). This means that we can also fine-tune the grinding to further improve the extraction efficiency.

The way to use pre-immersion, in fact, many friends have guessed the way to use pre-immersion in the above explanation in Qianjie. That's right! Light-roasted and freshly roasted coffee beans can be used as pre-soaking objects. Light-roasted coffee beans are difficult to extract because of their high density. Therefore, we need to use finer grinding to increase the water contact surface area of coffee powder, so as to improve the extraction rate. However, it is often easy to grind too fine, resulting in a slow flow rate of extraction, and the process is more difficult to be controlled.

Then, by pre-soaking, we can increase the flow rate and make the extraction more efficient at the same time; the same is true for freshly roasted coffee beans, but relatively speaking, Qianjie will be more recommended to put them into use. As the characteristics of each bean and each machine are different, there is no standard for pre-soaking time and pressure adjustment, which needs to be adjusted according to your own machine and beans.

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