Why Some Grocery Stores Tuck In Potatoes At Night

It sounds like a child's notion of what might happen on the night shift at the local supermarket. What do you mean, grocers tuck in their potatoes at night? Do they tenderly pull the covers up over their darling tuber heads, bidding them sweet dreams? Do they read "Goodnight Moon" to the cans of Campbell's soup? Do they leave a glass of warm milk out in the dairy aisle? (We can keep going, we have a dozen more of these.) As whimsical as it may sound, there's actually a pretty solid reason why grocery store owners might cover up their taters. By keeping the light from shining on the potatoes, they can keep their produce fresh and unspoiled. After all, potatoes that aren't in the right state can make you sick.

It's easy to forget these days, but potatoes are part of a family of plants that are ... well, poisonous. Potatoes (not to mention tomatoes, as well as other plants like tobacco and peppers) are part of the nightshade family, which contain alkaloids that can cause nausea, diarrhea, and fever. The potatoes you see in the supermarket produce aisle don't have a lot of alkaloids in them, but if they turn green, that's a sign that there are higher than usual levels of a toxic alkaloid called solanine.

Now, chances are that green potatoes won't kill you. You would have to eat several pounds of them to get seriously ill, and they taste bitter enough that you'd probably decide it wasn't worth it well before that point. But it's something you want to avoid, and grocers covering up their potatoes at night is one way to do it.

When potatoes turn green after being exposed to light, that's because of the presence of chlorophyll, the same chemical that makes grass and leaves green. Although the chlorophyll is harmless by itself, its presence is a telltale sign of solanine in potatoes. By covering up the potatoes, grocers are making sure they stay nice and brown for your eating pleasure. (It's the same thing you might do by keeping potatoes stored in a cool, dry place.) The curious nighttime ritual just makes it that much easier for you to enjoy scrumptious baked potatoes and crispy homemade french fries without being, you know, poisoned.