Mushroom is a kind of wild mushroom from Inner Mongolia grassland, usually growing next to sheep bones and dung. Mushrooms usually have a short shelf life, and mushrooms are no exception, and are prone to darkening inside. If the blackening is caused by oxidation, spore maturation, etc., it usually does not affect consumption; if the blackening is caused by decay or mold, it is not edible. If the mushroom only has a small amount of black spots in the cap, no abnormal odor and the mushroom body is still elastic, it is usually edible, but the nutritional value may be reduced. If the mushroom gills are black, it may be due to oxidation and spore maturation due to long storage time, it is also edible, but the taste and nutritional value may be affected. However, if the inside of the mushroom or the stalk is black, or even all the mushrooms are black, or there is a sour smell, the mushroom body is less elastic and sticky to the touch, etc., it means that the mushroom is rotten and bad, and it is not edible, otherwise it may lead to food poisoning and even life threatening. When buying and preserving mushrooms, you should pay attention to selecting fresh mushrooms and choosing the right preservation method to avoid them from turning black. When buying mushrooms, choose mushrooms that are relatively intact, with no rottenness, spots or water stains on the surface, and with no sticky feeling and normal color when touched by hand. After purchase, you can cut the mushrooms and drizzle them with citric acid water to slow down the browning reaction, or use a plastic bag to keep them out of the air to avoid oxidation, but be careful not to seal them, as high humidity can also accelerate their decay. You can also store mushrooms in the freezer of the refrigerator.