Experts recommend potatoes be stored at a temperature between 45 and 50 degrees Fahrenheit, and that onions be stored in a cool, dry place.
Potatoes especially should be kept out of the refrigerator. When stored at temperatures cooler than 45 degrees, starches in a potato begin to break down into sugars. Note: This is not how you make a sweet potato. The accumulation of sugars will cause the potato to darken when cooked. If you do have cold potatoes, it’s recommended that they be warmed gradually at room temperature before cooking to reduce the sugar levels and the risk of discoloration.
Potatoes also store better in high humidity — as high as 90 percent. Not surprisingly, a root cellar would be the perfect place for potatoes. Barring that, store in the coolest, most humid place you can. But not the fridge.
It’s also a good idea to keep potatoes in the dark. Overexposure to light can cause a buildup of solanine, an alkaloid that potatoes naturally produce to repel insects. Light also causes an increase in chlorophyll, which gives a green hue. So, potatoes that have a green tinge also likely have higher levels of solanine, which is toxic at high levels.
Actual illness is rare because not only are solanine levels usually quite low, but because solanine actually causes cooked potatoes to taste bitter. Luckily, solanine tends to stay near the surface. Peeling off green areas of a potato will also remove any solanine.
Potatoes that are stored too long or in too warm of a place will often sprout and begin to shrivel. If that happens, it’s time to throw them out. Potatoes with just a few sprouts can be salvaged by cutting them out.
Onions need a lot less humidity — ideally, 65-70 percent — but just as much ventilation as potatoes. In fact, the National Onion Association says not to store onions in plastic bags, because the lack of air movement will cause them to go bad more quickly. Common yellow onions are hardier and will store longer than other types. White onions and sweet onions are moister and more perishable, and to keep them longer, the association suggests storing them in the refrigerator, but wrapped in paper towels first to keep dry.
Chow Line is a service of Ohio State University’s College of Food, Agricultural, and Environmental Sciences and its outreach and research arms, Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH, 43210-1043, or [email protected].