Foods like sweet potatoes have high water content, so their chances of spoiling are pretty high.
A quick visual inspection of a sweet potato should reveal if it is bad or not. But sometimes, spoiled sweet potatoes may look like they are fresh.
Sweet potatoes that have gone bad may have a bitter and acrid taste. If this is the case with your sweet potato, you should discard it at once.
Fresh sweet potatoes are always firm and hard to the touch. When your sweet potatoes feel soft and mushy, they have gone bad.
Another sign of spoilage in sweet potatoes is mold or black rot. Mold and black rot are both fungal diseases, and they cause the insides of sweet potatoes to rot.
Mold or Black Rot