Choose firm, dark, smooth sweet potatoes without wrinkles, bruises, sprouts, or decay. Even if cut away, a decayed spot may have already caused the whole potato to take on an unpleasant flavor.
Sweet potatoes spoil rapidly. To keep them fresh, store them in a dry, cool (55-60º) place such a cellar, pantry, or garage. Do not store them in the refrigerator, where they will develop a hard core and an "off" taste. If stored properly, sweet potatoes will keep for a month or longer. At normal room temperature, they should be used within a week of purchase. You may brush off any excess dirt before storing, but do not wash them until you are ready to cook them. It is the moisture from washing that will increase their spoilage.
Wash sweet potatoes well. Cook them whole whenever possible as most of the nutrients are next to the skin, and skins are easier to remove after they have been cooked. Pierce skin with fork. Place potatoes in a pan and cook in an oven heated to 375º F for about 45 minutes or until tender. Cool potatoes slightly before removing skins. Sweet potatoes can be cooked in a microwave oven to save time. Wash and pierce potatoes, then place them on a paper towel. The cooking time for 2 medium potatoes is on high for 5-9 minutes, and 4 potatoes, 10-13 minutes. Yellow and dark orange sweet potatoes can be used interchangeably in recipes. Try not to mix the two types in a single dish, because their different textures and cooking times may affect the outcome of the recipe. The yellow variety takes longer to cook than the orange and will be done at the upper range of cooking times.
Although sweet potatoes are harvested in August through October, they are available in supermarkets all year. Many stores feature them at Thanksgiving and Christmas. There are two varieties of sweet potatoes; the pale yellow with a dry flesh and the dark orange with a moist flesh. The dark orange variety is plumper in shape and somewhat sweeter than the yellow variety.
Yellow, dry-fleshed Orange, moist-fleshed