Sweet potatoes contaminated by black rot fungus (a type of mold) will develop dark brown to black patches on their surface. The toxins excreted by the black rot fungus contain ipomeamarone and ipomeamaronol, which cause the sweet potato to become hard and bitter. The highly toxic substances produced have a significant impact on the human liver. These toxins cannot be destroyed by cooking, steaming, or roasting. Therefore, eating sweet potatoes with black rot, whether raw or cooked, can lead to poisoning.
The symptoms of poisoning from moldy sweet potatoes include stomach discomfort, nausea, and loss of appetite. In severe cases, symptoms of poisoning include vomiting, dizziness, and weakness, numbness, or paralysis in the limbs. The fatality rate can reach 16%. There are two main methods for preventing poisoning from black rot sweet potatoes:
First, do not eat spoiled, hard, bitter sweet potatoes or moldy sweet potato chips.
Second, before storing sweet potatoes, their skins should be sun-dried. The storage cellar should be located in a high, dry, and leak-proof area, and the padding straw should be clean. Sweet potatoes grown in low-lying areas or those that have been flooded should be consumed as soon as possible and are not suitable for use as seed.