Demystifying the Purple Sweet Potato Family
When you see a stunning purple-fleshed tuber at the market, it's easy to assume they are all the same. However, the world of purple sweet potatoes is more diverse than it appears. While the Okinawan sweet potato is certainly a type of purple sweet potato, it is incorrect to use the terms interchangeably. The umbrella term 'purple sweet potato' includes several varieties, each with its own unique characteristics, including the Okinawan variety and the American-bred Stokes Purple®.
The Defining Features of Okinawan Sweet Potatoes
The Okinawan sweet potato, known as beni imo in Japan, is a famous variety celebrated for its high nutritional value and a staple in the diet of the Okinawan people, who are renowned for their longevity.
- Appearance: This variety is easily identified by its contrasting skin and flesh. It features a creamy, beige-colored skin that can sometimes be mottled with darker brown spots. When cut open, it reveals a vivid, deep purple interior.
- Flavor and Texture: Okinawan sweet potatoes have a mildly sweet, slightly earthy, and dry, starchy texture, often described as having notes of honey. When cooked, they become soft and creamy, making them perfect for mashing or desserts.
- Origin: Although named for the Japanese island of Okinawa, this sweet potato's origin traces back to Central and South America. It was introduced to Okinawa in the 1600s, where it thrived in the subtropical climate.
The Stokes Purple® Sweet Potato: A Different Cultivar
One of the most common purple sweet potato varieties found in the United States, alongside the Okinawan, is the Stokes Purple® sweet potato. Patented in 2006, this variety has distinct differences from its Okinawan counterpart.
- Appearance: The Stokes Purple® has a purple-tinted skin and a deep purple flesh that intensifies when cooked, providing a uniform purple color throughout.
- Flavor and Texture: This variety offers a mildly sweet flavor with subtle floral notes. Its texture is notably drier and denser than the Okinawan sweet potato.
- Origin: Unlike the Okinawan variety, the Stokes Purple® was developed in North Carolina and is primarily grown in California for the US market.
Comparison of Key Purple Sweet Potato Varieties
| Feature | Okinawan Sweet Potato (Beni Imo) | Stokes Purple® Sweet Potato | Murasaki Sweet Potato (Japanese) | Ube (Purple Yam) |
|---|---|---|---|---|
| Skin Color | Creamy beige or off-white | Purple-tinted or light lavender | Reddish-purple | Brown, bark-like skin |
| Flesh Color | Vibrant, deep blue-purple | Deep purple | Creamy white | Vibrant purple, speckled purple |
| Flavor Profile | Mildly sweet with notes of honey | Mildly sweet with subtle floral notes | Very sweet with brown sugar and vanilla notes | Sweet, nutty, vanilla notes |
| Texture (Cooked) | Creamy and somewhat dry | Dry and dense | Starchy and moist | Moist, sometimes mealy or fibrous |
| Botanical Family | Morning Glory (Ipomoea batatas) | Morning Glory (Ipomoea batatas) | Morning Glory (Ipomoea batatas) | Yam (Dioscorea alata) |
| Origin | Introduced from South America to Okinawa in 1600s | Developed in North Carolina, patented 2006 | Developed in Louisiana, released in early 2000s | Native to Southeast Asia |
The Nutrient Power of Purple Sweet Potatoes
What unites all these purple-fleshed varieties is their nutritional powerhouse status, particularly due to high levels of anthocyanins. These potent antioxidants are responsible for the vegetable's color and provide numerous health benefits. Anthocyanins have anti-inflammatory, anti-cancer, and anti-diabetic properties. The Okinawan sweet potato, in particular, is noted for its ability to help regulate blood sugar, contributing to the longevity of the island's population. Furthermore, purple sweet potatoes are rich in dietary fiber, manganese, and vitamins A and C.
Cooking with Different Purple Sweet Potatoes
The best cooking methods vary depending on the sweet potato's texture. The creamy and slightly drier Okinawan sweet potato is excellent for mashing, baking, and making creamy dessert fillings like Haupia pie. Its drier texture is ideal for achieving a fluffy result. The denser Stokes Purple®, with its floral notes, also holds up well to baking and roasting, but a longer cooking time is often recommended to soften its texture. For a savory application, the Stokes Purple® can also be incorporated into stews or used to make crostini. Regardless of the variety, the cooking process enhances the natural sweetness and vibrant color, making them a visually appealing and healthy addition to many dishes.
The 'Yam' Misconception
It is also worth noting the frequent confusion between sweet potatoes and yams, a distinction that is especially relevant with purple varieties. A true yam is a tropical tuber with a rough, bark-like skin and starchy flesh that is botanically unrelated to the sweet potato. The popular Filipino ube is a true purple yam, not a sweet potato, but the terms are frequently, and incorrectly, used interchangeably. Historically, the mislabeling of sweet potatoes as yams in the US was a marketing tactic to differentiate orange-fleshed varieties.
Conclusion
In summary, while all Okinawan sweet potatoes are a type of purple sweet potato, the reverse is not true. The term encompasses a range of distinct varieties, with the Okinawan and Stokes Purple® being two of the most common. The Okinawan is characterized by its beige skin and sweet, dry flesh, while the Stokes Purple® has purple skin and a denser texture. Both offer exceptional nutritional benefits due to their high anthocyanin content. Understanding these differences allows cooks to select the best variety for their culinary applications, maximizing both flavor and nutritional impact.
Where to Find Purple Sweet Potatoes
If you are searching for these unique tubers, your best bet is to check specialty grocery stores, natural food markets, and Asian food stores. The availability may also vary by season, though Okinawan sweet potatoes are often available year-round.
Here is a guide to selecting and storing sweet potatoes to help you make the most of your purchase.
