The difference between steaming and steaming: without steaming, the extraction is easy to be less than the difference of water injection after hand steaming.

The difference of steaming or not: without steaming, the extraction is easy to be insufficient.

Steamed coffee powder, coffee powder will first dissolve some high concentration coffee liquid because it seeps into some hot water, so it is easier to extract some soluble substances of coffee during the second water injection, and some gases in the coffee powder have been discharged at the same time of steaming, so it is less likely to be disturbed by gas discharge during brewing extraction in order to achieve stable and uniform extraction.

If there is no steaming, it is easier to extract only the ingredients on the surface of the coffee powder, while the internal substances are not easy to be extracted, and because some gases in the coffee powder have not been discharged at the beginning, the time to float on the surface will be longer than that of steaming, resulting in insufficient extraction and lighter concentration of coffee.

After steaming, the difference of water injection by stages:

The concentration of water injection is high, and the concentration is low without water injection.

Undivided water injection: after steaming, continuous water injection until the required amount is stopped.

Step-by-step water injection: after the end of steaming, water injection will be divided into several times. after each stop, before the water level reaches the coffee powder noodle, hot water will be injected until the required amount is reached. (note 2)

As to why there is a difference in concentration between the two? First of all, let's briefly explain the way the liquid spreads, that is, the liquid with higher concentration will move to the liquid with lower concentration, and dissolving the high concentration coffee into the water is of course a kind of diffusion effect, so it is said before that the second injection after steaming, the high concentration coffee liquid dissolved first will move to the low concentration hot water.

Therefore, if we take step-by-step water injection, we will bring some high-concentration coffee liquid into the low-concentration hot water that has just been injected, so it will cause continuous extraction of high-concentration coffee liquid, but it is also relatively easy to extract the astringent odor. And in the process of water injection, the force of the water flow will disturb the coffee powder deposited at the bottom, so pay more attention to the water injection. Avoid extractive and astringent flavors. On the contrary, undivided water injection is adopted to retain some coffee liquid with higher concentration than hot water, so the concentration balance may even occur during extraction.

No matter which way, the extraction time is too long, it will bring out the bitter mixed taste (figure 2). This is because when the extraction is too long, almost all the good taste is extracted, and most of the bad taste is left behind. And the liquid concentration will continue to dissolve the bad taste in order to achieve balance. In fact, in the operation, which way to take can be decided according to the taste preference and the condition of beans.