[Violet Yam, Water Yam; Ube, Halaya (Philippine); Ratalu (India); Rasa valli kilangu (Tamil); Uhi (Hawaii); Ji, Ji abana, Isu ewura (Nigeria); Dioscorea alata]
Native to Southeast Asia, there are many cultivars of this yam, varying from deep purple to white. Intensely purple varieties are very popular through South and Southeast Asia, while most grown in Africa are white. These are the most common yam in Africa, but are little available in North American markets, even in Los Angeles with our large Philippine population. They are listed as noxious weeds in a few southeastern states, particularly Florida. The purple color comes from anthocyanin flavonoids, which have antioxidant properties, but how well these survive digestion is debatable. Photo by Obsidian Soul distributed under license Creative Commons Attribution-ShareAlike v3.0 Unported.
More on Yams.
Uses: Because it is quite sweet, this yam is often used in making confections and desserts, particularly in the Philippines and India. The color also works well for these applications. In the Philippines it is often grated, mixed with coconut milk and cooked down into a bright blue jelly. In Gujarati, India it is used in mixed vegatble dishes, and in Vietname it is used in a popular soup.
Buying: These can now be had from a few on-line sources. Caution: Philippine markets and some other Asian markets have bins of "Purple Yams" with light beige skins. They are Okanawan Sweet Potatos, not yams at all. They are purple inside, but not nearly as intensively as the real Purple Yam, and they are not as sweet.
Storing: These will store in a cool dark place similarly to potatoes, for a month or more.
Cooking: Cooked, its purple color darkens to deep violet.
Purple Yam Flour
This flour is used in the Philippines to produce purple Lumpia wrappers and similar applications. It is available from Philippine markets here in Los Angeles, but at a high price. Meager 4.06 ounce packets cost about 2017 US $4.69 depending on brand and store.