Brain Fuel

Author Essay

What causes the often-seen green discolouration in potatoes?
 
Exposure to light. The green tint often seen near the surface of potatoes is due to chlorophyll, the pigment in plants that makes photosynthesis possible. Essentially, when potatoes are exposed to excessive light, they will try to photosynthesize; in other words they will try to sprout and grow into potato plants. The green colour is completely harmless, but another substance, called solanine, forms at the same time as chlorophyll. The theory is that this natural toxin forms as the potato tries to protect itself against pests and fungi during the critical sprouting process. Solanine, which falls into the family of compounds known as glycoalkaloids, can be toxic to humans. One would have to eat a fair amount of green potatoes to experience serious toxic effects, but even small doses can cause stomach problems. It is best to peel away the green, which will remove most of the solanine, which tends to concentrate near the surface of the tuber. The best way to avoid discoloration and potential health problems is to keep the potatoes out of the light and store them at a cool temperature. The production of solanine involves an enzymatic reaction that proceeds slowly at low temperatures. So don’t worry about a little green discoloration in your potatoes, but do not go out of your way looking for green potatoes to eat.