The difference between soft flour and strong flour is classified based on how much viscoelasticity the dough becomes when water is added to the flour and kneaded together. This viscoelasticity is caused by two types of proteins contained in wheat (glutenin and gliadin), and when water is added and kneaded, it becomes "gluten" with a mesh-like network. If the protein content is low, the dough tends to be soft and soft, and if the protein content is high, the dough tends to be highly viscoelastic. In Japan, flour is classified in descending order of protein content as ``weak flour'', ``medium flour'', and ``strong flour''.
As for the size of the particles, the "soft flour" is fine, the "medium flour" is slightly fine, and the "strong flour" is rough. For this reason, when making confectionery and other items, powder is used to prevent the dough from sticking to the surface.