Published February 1, 2005.
What's the best way to store potatoes?
Since potatoes seem almost indestructible compared with other vegetables, little thought is generally given to their storage. But because various problems can result from inadequate storage conditions, we decided to find out how much difference storage really makes. We stored all-purpose potatoes in five environments: in a cool (50-60 degrees), dark place; in the refrigerator; in a basket near a sunlit window; in a warm (70-80 degrees), dark place; and in a drawer with some onions at room temperature. We checked all the potatoes after four weeks.
As expected, the potatoes stored in the cool, dark place were firm, had not sprouted, and were crisp and moist when cut. There were no negative marks on the potatoes stored in the refrigerator, either. Although some experts say that the sugar level dramatically increases in some potato varieties under these conditions, we could not see or taste any difference between these potatoes and the ones stored in the cool, dark but unrefrigerated environment.
Our last three storage tests produced unfavorable results. The potatoes stored in sunlight, in warm storage, and with onions ended up with a greenish tinge along the edges. When potatoes are stressed by improper storage, the level of naturally occurring toxins increases, causing the greenish tinge known as solanine. Because solanine is not destroyed by cooking, any part of the potato with this greenish coloring should be completely cut away before cooking. In addition, the skin of the potatoes stored in sunlight became gray and mottled, while the potatoes stored in a warm place and those stored with onions sprouted and became soft and wrinkled. Sprouts also contain increased levels of solanine and should be cut away before cooking.
To determine if we could achieve even better results by storing potatoes with an apple, we stored two 5-pound bags of russet potatoes, one with an apple and the other without, in a dry, dark, cool, well-ventilated spot and checked on both bags every other day for eight weeks. The potatoes in both bags looked fine until the three-week point, when one of the potatoes stored without the apple began to sprout. Two weeks later all but one of the potatoes stored without the apple had sprouted.
By comparison, the potatoes stored with the apple remained firm and free of sprouts, though a great deal of condensation had built up in the bag. At the eight-week point the potatoes without the apple were largely soft, shriveled, and sad looking. The potatoes stored with the apple, on the other hand, were mostly firm (small soft spots had developed on two of them) and looked good.
Dr. Greg Porter, associate professor of agronomy, and Dr. Alfred Bushway, professor of food science and human nutrition, both at the University of Maine in Orono, concurred that the ripe apple gives off ethylene gas as it respires. Simply put, the ethylene gas, as well as other organic alcohols emitted by the apple, suppresses the elongation of the potatoes’ cells, which is what causes the sprouts to form.