Solanine is a poisonous substance that occurs naturally in potatoes and other members of the nightshade family, such as tomatoes and eggplants. A very small amount of solanine can be toxic, and in very large doses it can be fatal.
Signs of Solanine
In potatoes, the skin will turn green and there will be a very bitter flavor. Symptoms of solanine poisoning include diarrhea and vomiting.
[Also see: Food Poisoning Symptoms]
Preventing Solanine Poisoning
One of the triggers for solanine to develop in a potato is exposure to light, especially fluorescent light. Therefore, it's always best to store potatoes in a dark place, preferably between 50 F and 65 F. If potatoes must be stored in a lighted place, it's best to keep them in a brown paper bag loosely closed to allow for air circulation.
Dealing with Solanine in Potatoes
If green discoloration is seen on a potato, the green areas can be cut off, but for safety's sake, it's probably best to discard the whole thing. Deep-frying a potato in oil that's hotter than 320 F will render the solanine harmless.