Roasted Japanese Sweet Potato Recipe

The sweet potato (Ipomoea batatas) is a tropical root vegetable. In the United States, the name Japanese sweet potato typically refers to Japanese (and Japanese-inspired) varieties of sweet potatoes with purple skin and white flesh, which have a slightly drier texture and more mild sweetness than orange sweet potatoes. The differences in texture and sweetness are due to amylase, an enzyme that breaks starches down into sugars and is found in higher quantities in orange sweet potatoes.

One of the most popular varieties of Japanese sweet potatoes in the U.S. is the Murasaki sweet potato, developed by the Sweet Potato Research Station at Louisiana State University in 2008. Murasaki means “purple” in Japanese, and, in Japan, it also refers to the purple-fleshed Okinawan sweet potato.

Sweet potatoes originated in Central and South America and came to Japan via China during the early eighteenth century. Sweet potatoes are still known as karaimo (Chinese potato) in the Ryukyu Islands, where sweet potatoes first arrived. In Satsuma, sweet potatoes are known as ryukyu-imo (Ryukyu Islands potato). In the rest of Japan, sweet potatoes are commonly known as satsumaimo (Satsuma potato), suggesting that the sweet potato traveled from China to the Ryukyu Islands to Satsuma. In Japan, sweet potatoes are important not only as a vegetable but as a source of starch for alcohol.

Japanese sweet potatoes are a source of beta-carotene (a precursor of vitamin A), vitamin C, vitamin B6, fiber, potassium, and calcium. They contain slightly less beta-carotene than orange-fleshed sweet potatoes. Sweet potatoes contain about half as much protein as regular potatoes, and their glycemic index is about twice as high.

3 Ways to Cook Japanese Sweet Potato
Japanese sweet potatoes have a texture similar to russet potatoes and can be baked, boiled, steamed, or fried. Popular applications of Japanese sweet potatoes include:

1. 1. Yakiimo (baked Japanese sweet potato): In Tokyo, foil-wrapped sweet potatoes are commonly sold by street vendors and in grocery stores as a wintertime comfort food. These are traditionally cooked on hot stones until caramelized sugar bursts from the flesh. You can bake sweet potatoes in the oven for a similar effect.
2. 2. Daigaku imo (candied sweet potatoes): These deep-fried Japanese sweet potatoes are glazed with sugar syrup and sprinkled with sesame seeds.
3. 3. Sweet potato fries: Japanese sweet potatoes are a great choice for roasting since they get crispy (not mushy) in the oven. Try tossing sweet potato wedges with olive oil, salt, and black pepper for an easy side dish.