For many families, holiday dinners wouldn't be complete without mashed sweet potatoes. But sweet potatoes are a treat you can enjoy all year long: baked, boiled, roasted, mashed, pureed, sautéed, fried and in casseroles—not to mention soups and desserts.
Here's everything you need to know about selecting and storing sweet potatoes.
Selecting Sweet Potatoes
There are two main types of sweet potatoes available in U.S. supermarkets: the Jewel, which has orange skin and orange flesh, and the Red Garnet, which has a darker red skin and also orange flesh. These two are what are most commonly used in preparing traditional sweet potato dishes.
Other varieties feature tan or purple skin and tend to be starchier and less sweet. You might also see Japanese sweet potatoes in the store. They have whiter flesh and tend to cook up a lot like ordinary Russet potatoes.
One specimen you're not likely to see in the typical produce department is a true yam, which is a long, pale tuber with skin that resembles tree bark, and which is not even related to the sweet potato. The confusion stems from the fact that some growers use the word "yam" to describe their sweet potatoes, even though they are not that vegetable at all. If you see a tuber with orange flesh, it's a sweet potato, regardless of how it's been labeled.
When buying sweet potatoes, look for small to medium sized ones that are firm and smooth with no cuts or cracks.
How to Store Sweet Potatoes
Sweet potatoes stay fresh longest in a cool or room-temperature location, away from moisture, heat and light. Depending on your kitchen, this might be a kitchen cupboard (not situated directly next to your oven), or a dedicated pantry. Cupboards near the floor will stay cooler than ones that are higher up. The ideal temperature for sweet potatoes is between 50 and 60 F.
The reason for keeping your sweet potatoes in the dark is that if they're exposed to light, they think they're outside and will start to sprout.
As long as the location is cool, dry and dark, sweet potatoes will last up a month or longer, if the temperature remains between 50 and 60 F. Between 60 and 70 F, their shelf life diminishes significantly, but they'll still keep for up to a week. The upshot is that your sweet potatoes will generally last longer in the cooler months than they will when it's hot.
You should also resist the temptation to wash your sweet potatoes before storing them, as this will accelerate rot. If there's visible soil, go ahead and brush it away with a dry cloth or paper towel. Once you're about to cook them, of course, wash them as you normally would.
A quick note about onions, which require similar conditions for optimal storage. Storing onions near potatoes will cause the potatoes to sprout faster, due to the moisture the onions emit. So even though onions need to stay in your cupboard or pantry just like sweet potatoes, try to store them away from each other—at least on separate shelves.
Avoid the Refrigerator
And by the way, sweet potatoes shouldn't be stored in the refrigerator. The colder temperatures of the fridge, typically 40 F and lower, will cause changes to the starches in the potato, making the potato hard in the middle and producing an unpleasant flavor.
The one exception to this is if you've already peeled a sweet potato and want to save it for later. In this case, you can store it, tightly wrapped or in an airtight container, in the fridge, but use it as soon as possible—within 2 to 3 days is best.
A sweet potato that's been sliced in half but is otherwise unpeeled can still be stored at pantry temperatures. When you're ready to use it, you may want to slice off the cut section, but otherwise it should be fine, at least for a week or two.
And as for storing raw sweet potatoes in the freezer, it's not recommended; they'll be mushy, watery and stringy when thawed.
Freezing Sweet Potatoes
That doesn't mean you can't freeze sweet potatoes, you just need to cook them first.
One method is to slice them into whatever thickness of slices you desire, or dice them, then boil them until tender but still firm, usually 10 to 15 minutes, then cool and freeze in storage bags with all the air pressed out. A vacuum sealing system is ideal for this.
Another method is to cook (either by boiling or baking) and then mash the sweet potatoes, before slipping off the skins and mashing, along with a bit of lemon juice to limit unwanted browning, and freezing in plastic freezer bags.
You can even bake sweet potatoes and freeze them whole, wrapped in foil and then freezer-bagged. Sweet potatoes that are frozen using any of these methods will keep in the freezer for up to 12 months.