Ma (Korean yam)

Ma is the Chinese yam (Dioscorea polystachya), a twining perennial vine with heart-shaped leaves and an underground tuber whose shape, size and color vary by variety: long and club-like, short and stout, or round. It should not be confused with the orange sweet potatoes sold as "yams" in North America. The Sino-Korean names are seoyeo (薯蕷) and, in herbal medicine, sanyak (山藥, "mountain medicine"); the Joseon primer Hunmong jahoe already glosses the characters with the native word ma.

Ma has a place in one of Korea's oldest stories. According to the Samguk yusa, the future King Mu of Baekje was known as a boy as Seodong, "yam boy," because he dug and sold yams for a living, and he is said to have won over the children of Silla by giving them yams so that they would sing his song about Princess Seonhwa. The fifteenth-century Sejong sillok jiriji lists sanyak as a medicinal product and tribute from provinces across the country. Joseon famine manuals recommend it, and farming manuals such as Sallim gyeongje describe how to grow it. For centuries it was mostly dug from the wild; cultivation came later.

Today Andong in North Gyeongsang Province is the center of production. The northern district of Bukhu-myeon has grown yams as a cash crop for about a century, the area produces about 70 percent of the national harvest by local accounts, and Andong was designated a special yam zone in 2005. The short, firm yams grown there are traditionally used for medicinal preparations, while longer, softer, more watery types from other regions are sold for eating fresh.

Ma is steamed (in Andong, often served with honey), cooked into rice and porridge, brewed as a tea, and eaten raw: grated into a slippery paste or blended into majeup, a yam drink. Peeled flesh browns quickly in air as an enzyme acts on the amino acid tyrosine; a dip in vinegared water slows it.

• Easily digested starch: Korean references describe ma as containing digestive enzymes such as amylase and a slippery mucilage, which is why it can be eaten raw. Per the Korean Food Composition Table, it also provides potassium and fiber.
• Traditional tonic: In Korean herbal medicine sanyak is a classic tonic, said to strengthen energy and digestion. These are traditional uses, not established health effects of eating yam as food.
• Not a diet substitute: Yam is still a starchy carbohydrate food. People managing blood sugar should count it like other starches.
• Handling: Peeled yam is very slippery; hold it with a towel or the unpeeled end when grating. Some cooks also find the raw flesh makes their hands itch.