The extraction process of coffee is two steps.
The first step, it is moving the components on the surface of the coffee powder to the water. The speed at which these components are transferred is related to their own concentration. If the concentration of coffee components on the surface of the coffee powder is high and the concentration of coffee components in the water is low, the speed of ingredient transfer is fast. Therefore, at the initial stage of extraction, the transfer of coffee components to water is fast, and with the change of time, the speed will be slower and slower. The amount of coffee dissolved in the water in the first 1 minute of brewing will be much greater than the amount dissolved in a certain minute some time later.
The second step, is to make coffee components moving from the center of the coffee powder to the surface. In the first step, the ingredients on the surface of the ground coffee have been dissolved in the water, so the concentration of the surface of the ground coffee has decreased. This triggers the second step - the movement of the coffee ingredients. In the second step, the components move more slowly than in the first step. What we say is that "the taste of coffee is different if the raw materials and brewing methods of coffee beans are different" is actually the impact of the second step of extraction.
