Why is the hot pot mushroom soup black?

First of all, it must be fungus soup. I have worked in a hot pot restaurant. Auricularia auricula has just been cooked to a thick khaki color, but it will turn black as soon as it is released. It should be oxidation (guess, or the concentration is getting higher? In short, it does not affect the taste). Instead, it is blended soup, which is easy to master both in appearance and taste. Any color you want. The best choice to save money and recover costs. There is no comparability in nutritional value, the former is beneficial and the latter is harmful.