Spice powder is a processed condiment. Usually it contains a variety of ingredients, some are used in dishes, and some are used in drinks and pastries. Different manufacturers and regions have different formulas, so they cannot be generalized. There is also powdered MSG, a low-grade MSG whose sodium glutamate content is only 75%, and the rest is salt. The flavor powder mentioned in general recipes is this kind of MSG. From your recipe, it looks like it is used for making Japanese noodles, but the dosage of five pounds seems a bit outrageous. There is a kind of shichimi powder in Japanese pasta that is specially used to mix udon noodles and soba noodles. The taste is mainly spicy and contains mustard seeds, tangerine peel, sesame, sansho pepper, hemp seeds, perilla, seaweed, green seaweed, ginger, etc.