Purple sweet potatoes (sometimes mistakenly called purple yams) are fun to cook with and can be used in many of the same ways as the more familiar orange or white sweet potatoes. Though some varieties have white skin, cutting one open will reveal their violet-colored surprise. Popular in some Asian and Latin cuisines, they add a brilliant pop of color to food and require just a few adaptations to cook.
What Are Purple Sweet Potatoes?
Purple sweet potatoes are root vegetables. The tubers taper to points on both ends and are members of the Ipomoea genus, just like other sweet potatoes (yams are of the genus Dioscorea). There are two main varieties—Okinawa (white skin) and Stokes (purple skin)—though they share the characteristic of having a deep purple flesh. The color comes from anthocyanins, the same pigment that gives cherries, strawberries, purple carrots, and other vegetables their color. These sweet potatoes are easy to prepare and cook. They're not as easy to find as regular sweet potatoes and are more of a specialty item, so they will cost a little more.
Sweet potatoes that have brown, red-orange, or white skin with orange or white flesh are native to Colombia and southern Central America. After Columbus' discoveries, they were brought to Asia, and varieties with white skin and speckled pale purple flesh were developed on the Japanese island of Okinawa. Today, they are widely grown in Hawaii and exported to the United States mainland where they are popular with Asian and Latino communities.
How to Cook With Purple Sweet Potatoes
Purple sweet potato skins are edible, though some recipes recommend peeling them first. When cooking, purple sweet potatoes will take longer than regular sweet potatoes. You will need to bake them anywhere from 90 minutes to 2 hours at 350 F to make them pleasingly moist.
Purple sweet potatoes are wonderful boiled, steamed, or baked alongside regular sweet potatoes. They can be used in many of the same ways you’d use an orange or white potato, and the colorful result puts a fun spin on mashed potatoes, fries, and soups.
If you're going to use this sweet potato in baked goods, you do need to be cautious about recipes that include baking soda. Combining the two ingredients may turn the potato's flesh green.
What Does It Taste Like?
Purple sweet potatoes have a rich, almost winey flavor with a creamy texture. They are denser and drier than regular sweet potatoes, which is why moist cooking methods and longer times are recommended.
Purple Sweet Potato Recipes
While you may be hard-pressed to find recipes that specifically call for purple sweet potatoes, they can work in nearly any recipe that uses regular sweet potatoes. Just keep in mind the extended cooking time when using them as a substitute.
Where to Buy Purple Sweet Potatoes
Okinawan sweet potatoes enjoy a year-round season while the Stokes Purple variety is typically available from September through June. Like other sweet potatoes, however, the peak season for the purple varieties is during the fall and winter months. They may not be available in every grocery store, depending on where you live. You'll have the best luck at specialty markets, including those that cater to Asian foods. Like other potatoes, they are sold by the pound, either loose or weighed out in bags (3 pounds is common). You can also buy them in larger bulk quantities at some stores or online. You can grow purple sweet potatoes at home, though availability of the slips or shoots for planting is limited and not always easy to find. The Okinawan variety needs a similar climate to Okinawa, such as Hawaii, while Stokes Purple is a better choice for home gardens on the U.S. mainland.
Look for purple sweet potatoes that are firm. Avoid any with soft or brown spots, sprouts, or wrinkled skin.
Sweet potatoes, in general, do not store as well as regular potatoes. Avoid bruising these potatoes as the slightest damage can cause the entire sweet potato to go bad. You can keep them at room temperature for about a week. For longer storage, keep them in a dry, dark, and cool place with good ventilation and use within a few weeks. Storing any sweet potato in the refrigerator can throw off the flavor and lead to a very hard center.
Cooked sweet potatoes can be stored in an airtight container for a week. Like other sweet potatoes, you can also freeze them after cooking, whether whole and baked or as a casserole.
Nutrition and Benefits
The same anthocyanins that make food look pretty are touted as having beneficial health effects. Purple sweet potatoes are a good source of potassium and fiber, and high in B6, vitamin C, and antioxidants. Additionally, they have a low glycemic index, which is why sweet potatoes (of any variety) are often preferred for diabetic diets.
Purple Sweet Potatoes vs. Purple Yams
Sweet potatoes are grown underground while yams grow on a vine above the ground, though yams do look like a tuber. The two are commonly confused and mislabeled at the market, so most people in the U.S. have never eaten an actual yam (native to Africa). There are purple varieties of both vegetables. The purple yam is the Filipino ube or ubi, and it is very rare to find it in the United States. It has a darker, rougher-looking skin that's brown and reminiscent of tree bark. This vegetable is a major crop and food source in the Philippines. It is also made into a powder, which is then used in Filipino desserts that are unmistakable with their bright purple color.
The purple sweet potato goes by a few names, and there are two common varieties. One is the Okinawan sweet potato, which is called beni imo in Japan; it's also known as the Hawaiian sweet potato or uala. The other is Stokes Purple, a name patented by a North Carolina farmer around 2006. The biggest difference between the two varieties is that the Stokes version has a light lavender skin and bright lavender flesh, while the Okinawan has a creamy-white skin with deep purple flesh. Depending on where you live, it might be easier to find Stokes Purple at the markets.