The plant known in the Ainu language as aha or eha (Amphicarpa bracteata Edgeworthii var. Japonica) most often grows spontaneously in the forests of the mountainous areas and on the banks of the rivers of the island of Hokkaido but also in the Honshu, Shikoku and Kyushu islands of Japan.
In the Ainu language, aha means “fruit that has come to fruition underground” but is primarily known as “yabumame” or “Chinese hog-peanuts”.
The plant is an annual, climber and belongs to the leguminosae family. It is quite widespread in Asia. The lower part of the stem is thicker, while the upper part is thin, in order to favour its growth in length. In fact, it can extend to about 1 meter, entangling itself on the surrounding vegetation. It is peculiar as it grows three types of flowers. The aerial flowers, which makes it easily recognisable, are about 2 cm long and have a typical butterfly shape. The petals are whitish with dark purple ends. While the other two flowers are less visible and both grow on the ground and on the part of the stem that is underground, their main feature is cleistogamy, meaning the flowers do not open and they pollinate themselves. This adaptation strategy is believed to be due to the inhospitable environment in which they grow up.
The plant is a particularly interesting part of the diet of this population, as it produces small beans that grow underground. Their colour is lilac, with brown or black streaks and the weight of the individual seed is about 10 grams. The sweetish taste is similar to that of broad beans. The harvest takes place in April, when the snow begins to melt, and it is possible to dig up the ground. The Ainu use the climbing plant as a reference, to choose the right place to dig up to the roots, and then collect the beans one by one.
The bean is very versatile in the kitchen. It can be dried, peeled and boiled on its own or cooked with rice (aha mesi). When paired with rice and Japanese millet, it is called Chisassuiepu and is used as a ritual offering.
In the traditional diet of the Ainu, the aha bean has always been an important food. However, in-depth studies on its nutritional and bioactive components have never been conducted. A recent study by the University of Hokkaido has shown that this bean is rich in antioxidants and it has not been ruled out as being used as a functional food in the future.
Today aha is not used very much by the Ainu because the harvest and preparation necessary for cooking take a long time, while substitutes such as soy or red beans are easy to consume.
Excessive urbanisation, especially around Sapporo, has made it difficult to find aha as the environment in which they grow has been drastically reduced. Furthermore, the number of Ainu people has decreased significantly, and their food culture is facing a complex transition of traditional knowledge from community elders to younger generations.
With the spread of westernized diets, Ainu food is rarely seen outside of ceremonies.
The Slow Food Community Ainu Women for the safeguard of Ainu Food Culture is working to pass on traditional foods to the next generations based on the concept of "circulation while being grateful for the blessings of nature" passed down from their ancestors. They also create new creative dishes that utilize Ainu ingredients and food culture, and pass them on to as many people as possible. In this way, Ainu women are preserving nature and traditional foods.