The sweet potato is already the most nutritious of all vegetables, but its nutrient content can be significantly increased by running a small electrical current through it, Japanese researchers have reported. The Center for Science in the Public Interest once ranked sweet potatoes No. 1 of all vegetables in terms of nutrition, well ahead of No. 2 white potatoes. More than 95% of the global sweet potato crop is grown in developing countries, where the vegetable provides a crucial part of the diet. The new research provides a simple, inexpensive way to improve its value.
Chemist Kazunori Hironaka of the University of the Ryukyus in Nishihara, Okinawa, Japan, and his colleagues had previously shown passing an electrical current through white potatoes could increase their levels of polyphenols -- important antioxidants that protect people from diseases and the effects of aging -- by 60%. Hironaka reported Monday at a Philadelphia meeting of the American Chemical Society that the procedure works for sweet potatoes as well.
The potatoes are immersed in salt water and a small current passed through the solution for five minutes. The team found that the best results were obtained with a current of 0.2 amps, which increased the antioxidant level by 40% and the concentration of polyphenols by 60%. Sweet potatoes already have as much as seven times the antioxidant level of white potatoes, so the added boost makes them potentially even more valuable in developing countries where supplements and healthy foods are not always readily available. The treatment does not change the taste of the potatoes and could easily be performed by small farmers, he said. Hironaki recommended steaming the potatoes to retain the maximum quantity of nutrients when cooking them.