Whether or not you can eat a blackened yam depends on whether or not the yam is spoiled. If the surface of the yam is blackened and the inside is white after peeling or cutting, then it can be eaten; if it is not blackened on the surface, then it cannot be eaten. If it is due to the yam after peeling did not use in time, resulting in contact with the oxygen in the air is oxidized, resulting in the blackening of the surface of the yam, this is a normal oxidation phenomenon, at this time the yam can be eaten. If the yam is black is the surface of the black mycelium or spots, in peeling, cutting still black, while there is also ulceration, abnormal rotten odor and other phenomena, it indicates that the yam has deteriorated, can not be eaten. It is recommended to develop a good dietary habits, food that is bought and eaten, such as eating a certain kind of food after the symptoms of discomfort, the need for timely medical standardized treatment.