one way valve said that erosion occurs in a pressure environment where the water is filtered the coffee powder by the pressure in the confined space. During the process, some non-soluble substances, fibers and proteins are also extracted. So the taste of coffee is usually heavy. In addition, “erosion” can improve the rate of “diffusion”. During brewing process, waggling, shaking, or stirring coffee powder also achieve partial erosion effect.
Firstly is gravity. The coffee is extracted by gravity, the diffusion occurs in the extraction process is moderate, and degree of “erosion” is very low. The gravity can make the taste of coffee more delicacy, the acidity higher.
Secondly is pressure. The coffee is extracted by pressure, the diffusion occurs in the extraction process is higher, and degree of “erosion” is medium to low. The pressure makes the taste of coffee heavier.
Thirdly is soaking. The coffee is extracted by soaking, the diffusion occurs in the extraction process is highest, and degree of “erosion” is multiple, so the flavor of coffee is more complex, and the taste is more complete.
At last is siphon type. That is siphon coffee; the degree of “erosion” is moderate to low. Because there is no additional pressure is applied, the taste of siphon coffee is richer and more delicacy than the coffee extracted by pressure. In addition, siphon coffee uses a soaking method at the same time, which has a higher degree of "diffusion".
At the same time, another reason for the complex taste of siphon coffee is that the higher water temperature, so it can extract more soluble substances in coffee.