Okinawan Sweet Potato
["Purple Yam" (improper), Hawaiian Sweet Potato; Uala (Hawaii); Kara-mmu (Japan); C. Ipomoea batatas cv. ayamurasaki ]
These light beige skinned sweet potatos were carried from the American tropics to the Philippines and China by the Spanish, reaching Okinawa around 1600. They are now grown on the Japanese main islands, but still considered "Okinawan", with the Murasaki considered "Japanese". They are quite available in Asian markets here in Los Angeles, always confusingly labeled "Purple Yam". Real Purple Yams are not currently much available in North America. The purple color comes from anthocyanin flavonoids, which have antioxidant properties, but how well these survive digestion is debatable.
Young leaves and shoots are also edible and called Kandaba in Okinawa. They are used in miso soups and as a vegetable side dish, or in recipes as are other greens.
More on Sweet Potatoes.
This sweet potato is moderately sweet and can be used the same as white or orange sweet potatoes. The flesh is a bit starchy, closer to a real yam than most sweet potatoes.
Uses: This sweet potato is used as an imperfect substitute for real Purple Yams, not as sweet or as purple. It can be used the same as regular sweet potatoes as a general vegetable, often in stews and the like, or baked whole. It is good for sweet potato recipes where the bright color would be a plus.
Buying: These are availbale in Philippine markets and other markets serving a Southeast Asian population, always mislabeled as "Purple Yams".
Storing: These will store in a cool dark place similarly to potatoes, for about 2 weeks.
Cooking: Cooked, its purple color darkens to deep violet. Cut into slices or cubes, it cooks in 10 minutes and begins to break up at 15 minutes. Fine for baking and most other sweet potato uses.