No, besides starch, there is protein in the flour. However, I can teach you how to make water starch. Wrap the flour with washing gauze and wash it with clear water. A lot of white things will come out. After washing, there will be a mass of things in the gauze, such as protein. Clarify the water, pour out the excess water, and mix well, which is what is in the water starch gauze. Actually, it can be steamed to make gluten, which we eat in cold noodles.