The Japanese yam, or nagaimo (Dioscorea opposita or Dioscorea batatas), is native to Southeast Asia and has been cultivated in Japan since the Jomon period (14,000BC – 300BC). Japanese yams are slick or slimy when cut and are crispy when eaten raw. These highly nutritious tubers are an exception to the rule that yams (Dioscorea) must be cooked to be edible. Japanese yams can turn brown where they have been cut – due to oxidation – but the change in color poses no problems for eating. To prevent oxidation, place cut pieces of Japanese yam in water with a little vinegar added. Hands can sometimes become itchy as a result of contact with raw Japanese yams. Vinegar and water, or lemon juice, will help to suppress this itchiness.
Text by Kitchen Nippon